docs(metadata): doc-type authoring guide + objectstack-ui skill coverage (ADR-0046)

Package docs (ADR-0046) shipped framework-side (collection + render) and a
showcase example (#1793), but the developer docs site and AI skills never
mentioned the `doc` metadata type. Close that gap:

- New guide content/docs/guides/metadata/doc.mdx — flat src/docs/*.md
  authoring, namespace-prefixed naming, the platform-level /docs/<name>
  routing model (no per-app/per-package URL nesting), cross-references,
  and the MDX/image build bans.
- List `doc` in the metadata index table + sidebar (meta.json).
- objectstack-ui skill: new "Docs — Package Documentation" section so AI
  agents author src/docs/*.md correctly (flat dir, prefix, CommonMark+GFM,
  link-don't-embed for dynamic content), plus description/tags coverage.

Docs/skill only — no package code. Frontend /docs route + nav entry remain
the objectui P2 follow-up.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: os-zhuang

content/docs/guides/metadata/doc.mdx

@@ -0,0 +1,159 @@
+---
+title: Doc Metadata
+description: Ship package documentation as metadata — flat src/docs/*.md files compiled into the manifest and rendered in the console
+---
+
+# Doc Metadata
+
+A **Doc** is a single page of package documentation. You write plain
+Markdown files in a flat `src/docs/` directory; `os build` compiles each
+one into a `doc` metadata item that ships inside the package artifact and
+renders in the console at `/docs/<name>`. Docs are also the grounding the
+AI assistant reads when answering questions about your package.
+
+Unlike `content/docs/` (which builds a standalone website), package docs
+are **package source** — they travel with the package, version with it,
+and are addressable as metadata like any Object or View.
+
+## Authoring: flat `src/docs/*.md`
+
+The normal way to author a doc is to drop a Markdown file in `src/docs/`:
+
+```
+src/docs/
+  crm_index.md            → doc name "crm_index"
+  crm_user_guide.md       → doc name "crm_user_guide"
+```
+
+The filename stem becomes the doc `name`. There is no directory taxonomy
+and no ordering file — the flat layout is what keeps cross-references
+stable (a link resolves by basename, never by path).
+
+### Frontmatter
+
+A leading YAML frontmatter block is optional. Only `title` is read:
+
+```md
+---
+title: User Guide
+---
+
+# Getting started with CRM
+...
+```
+
+The display title resolves in order: frontmatter `title:` → the first
+`#` heading → the doc `name`.
+
+## Doc Properties
+
+When a `*.md` file is collected, it becomes a `doc` item with this shape:
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| `name` | `string` | ✅ | Machine name (`snake_case`), from the filename stem. Must match `^[a-z][a-z0-9_]*$` and be **namespace-prefixed** |
+| `label` | `string` | — | Display title (from frontmatter `title`) |
+| `content` | `string` | ✅ | The Markdown body |
+
+You can also declare a doc programmatically with `DocSchema` in a stack
+definition's `docs` array, but the `src/docs/*.md` path is the convention
+— it gives you native editor and GitHub preview for free.
+
+## Naming and routing
+
+Doc names live in the same flat, instance-global namespace as the URL.
+The console route is **single-coordinate** — `/docs/<name>`, with no
+package or app prefix — so a doc has exactly one URL no matter who links
+it.
+
+That only works if names don't collide, so the build requires every doc
+name to be **namespace-prefixed**:
+
+```
+src/docs/crm_user_guide.md      ✅  package namespace is "crm"
+src/docs/user_guide.md          ❌  bare name — collides across packages
+```
+
+This is the same uniqueness rule the platform already applies to other
+named metadata (ADR-0048). Two packages that both ship `user_guide` would
+overwrite each other on the registry key and fail at install; the prefix
+makes the collision impossible.
+
+> **Routing model.** The viewer is platform-level: one global
+> `/docs/<name>` route resolves any doc regardless of which app you came
+> from. Anything that wants to *link into* docs — an app's navigation, a
+> registry package page, an agent's answer — does so with that same URL.
+> Per-app or per-package URL nesting is explicitly **not** the model
+> (it would give one doc many URLs and break cross-references).
+
+## Cross-references
+
+Link to a sibling doc with a plain relative Markdown link:
+
+```md
+See the [overview](./crm_index.md).
+```
+
+The console rewrites `*.md` links to `/docs/<target>` (anchors are
+preserved); in an editor or on GitHub the same link resolves natively.
+**Broken same-package links fail the build**, so references can't rot
+silently.
+
+## Markdown support
+
+Docs render **CommonMark + GFM** through a sanitizing pipeline. Supported
+out of the box:
+
+- Standard Markdown — headings, lists, tables, blockquotes, inline/fenced
+  code, links.
+- **Heading anchors** — every heading gets a slug id and a hover anchor,
+  so `#section` deep-links work.
+- **Syntax highlighting** — fenced code blocks are highlighted by
+  language.
+- **GitHub alerts** — `> [!NOTE]`, `> [!TIP]`, `> [!WARNING]`, etc.
+  render as callouts.
+
+Two things are **rejected at build time**, by design:
+
+- **MDX / embedded components.** Docs are publisher-supplied content
+  rendered inside the platform; executing authored code would cross a
+  trust boundary. Markdown is data, not code.
+- **Image references.** Images need a content-addressed asset service
+  (a later, additive concern). Until then, `![...](...)` fails the build
+  rather than producing broken `<img>` tags in a tenant.
+
+For dynamic content (a live flow diagram, a record table), don't try to
+embed a component — link to the metadata by URL instead. The platform
+renders the live view; the doc just points at it.
+
+## Example
+
+```md
+---
+title: CRM Overview
+---
+
+# CRM
+
+The CRM package manages accounts, contacts, and opportunities.
+
+> [!TIP]
+> New here? Start with the [user guide](./crm_user_guide.md).
+
+## Objects
+
+| Object | Purpose |
+| :--- | :--- |
+| `crm_account` | Companies and organizations |
+| `crm_contact` | People at an account |
+```
+
+Saved as `src/docs/crm_index.md`, this compiles to a `crm_index` doc and
+renders at `/docs/crm_index`.
+
+## Next Steps
+
+- See the in-repo authoring reference in the showcase package:
+  `examples/app-showcase/src/docs/showcase_docs_guide.md`.
+- Read [ADR-0046](https://github.com/objectstack-ai/framework/blob/main/docs/adr/0046-package-docs-as-metadata.md)
+  for the full design rationale and rollout phases.

content/docs/guides/metadata/index.mdx

@@ -49,6 +49,14 @@ Define access control and data visibility.
 | :--- | :--- | :--- |
 | [**Permission**](./permission) | Permission sets — object CRUD, field security, tab visibility | `*.permission.ts` / `*.permission.yml` |
 
+### Documentation Layer
+
+Ship package documentation that travels and versions with the package.
+
+| Metadata Type | Description | File Convention |
+| :--- | :--- | :--- |
+| [**Doc**](./doc) | Package documentation pages — flat Markdown, rendered at `/docs/<name>` | `src/docs/*.md` |
+
 ## How Metadata Works Together
 
 ```

content/docs/guides/metadata/meta.json

@@ -11,6 +11,7 @@
     "flow",
     "workflow",
     "validation",
-    "permission"
+    "permission",
+    "doc"
   ]
 }

skills/objectstack-ui/SKILL.md

@@ -2,9 +2,11 @@
 name: objectstack-ui
 description: >
   Author ObjectStack UI metadata — Views (list/form/kanban/calendar/gantt),
-  Apps (navigation), Pages, Dashboards, Reports, Charts, Actions. Use when
+  Apps (navigation), Pages, Dashboards, Reports, Charts, Actions, and
+  package Docs (`src/docs/*.md`). Use when
   the user is adding `*.view.ts` / `*.app.ts` / `*.dashboard.ts` /
-  `*.action.ts` files or designing a Studio-rendered UI surface, including
+  `*.action.ts` / `src/docs/*.md` files or designing a Studio-rendered UI
+  surface, including
   dataset-bound dashboard/report widgets. Do not use for: data schema (see
   objectstack-data), interactive screen flows /
   wizards (those are `*.flow.ts` with `type: 'screen'` — see
@@ -18,7 +20,7 @@ metadata:
   author: objectstack-ai
   version: "1.1"
   domain: ui
-  tags: view, app, page, dashboard, report, chart, action, widget
+  tags: view, app, page, dashboard, report, chart, action, widget, doc
 ---
 
 # UI Design — ObjectStack UI Protocol
@@ -37,6 +39,8 @@ App navigation, Dashboards, Reports, and Actions.
 - You need a **dashboard** with widget grids.
 - You are adding **reports** (tabular, summary, matrix, chart).
 - You are configuring **actions** (buttons, URL jumps, screen flows).
+- You are writing **package documentation** (`src/docs/*.md`) that ships
+  with the package and renders at `/docs/<name>`.
 
 ---
 
@@ -616,6 +620,90 @@ export const LeadDetailPage: Page = {
 
 ---
 
+## Docs — Package Documentation (ADR-0046)
+
+A **Doc** is a page of package documentation shipped *as metadata*. You
+author plain Markdown in a flat `src/docs/` directory; `os build`
+compiles each `*.md` into a `doc` item that travels inside the package
+artifact and renders in the console at `/docs/<name>`. Docs are also the
+grounding the AI assistant reads about a package.
+
+```
+src/docs/
+  crm_index.md         → doc "crm_index"      → /docs/crm_index
+  crm_user_guide.md    → doc "crm_user_guide" → /docs/crm_user_guide
+```
+
+### Authoring rules (each enforced by `os build`)
+
+1. **Flat directory.** Every `.md` lives directly in `src/docs/`;
+   subdirectories are a build error. Flatness is what keeps links stable
+   — a reference resolves by basename, never by path.
+2. **Namespace-prefixed filename.** The filename stem becomes the doc
+   `name` (`^[a-z][a-z0-9_]*$`) and must start with the package namespace
+   (`crm_…`). Names share one flat, instance-global space with the URL, so
+   a bare `user_guide` would collide across packages and fail at install
+   (ADR-0048).
+3. **Title** resolves: frontmatter `title:` → first `#` heading → `name`.
+4. **Pure Markdown.** CommonMark + GFM only, plus heading anchors, fenced
+   code highlighting, and GitHub alerts (`> [!NOTE]`, `> [!WARNING]`, …).
+   **MDX and image references are rejected at build time** — docs are
+   publisher content rendered inside the platform (no authored code across
+   the trust boundary; images await a content-addressed asset service).
+5. **Cross-references** use plain relative links — `[overview](./crm_index.md)`.
+   The console rewrites `*.md` → `/docs/<target>` (anchors preserved);
+   broken same-package links fail the build.
+
+### Routing model — platform-level viewer, opt-in entry
+
+The viewer is **platform-level**: one global `/docs/<name>` route
+resolves any doc regardless of which app you came from. The URL is
+**single-coordinate** — no package or app prefix — so a doc has exactly
+one URL. Do **not** design per-app or per-package doc URLs; that gives one
+doc many addresses and breaks cross-references.
+
+To surface a doc inside an app, add a navigation item that **links into**
+that global URL. There is no dedicated `doc` nav-item type yet, so use a
+`url` item pointing at `/docs/<name>`:
+
+```typescript
+navigation: [
+  { id: 'nav_help', type: 'url', url: '/docs/crm_user_guide',
+    label: 'User Guide', icon: 'book-open' },
+]
+```
+
+A platform-level "Documentation" portal (browse/search all docs by
+package) is a later, additive concern — author-side, nothing to model now.
+
+> **Dynamic content.** Don't try to embed a live component (a flow
+> diagram, a record table) in a doc — there is no inline SDUI. Link to the
+> metadata by URL; the platform renders the live view, the doc points at it.
+
+### Example
+
+```md
+---
+title: CRM Overview
+---
+
+# CRM
+
+Manages accounts, contacts, and opportunities.
+
+> [!TIP]
+> New here? Start with the [user guide](./crm_user_guide.md).
+
+| Object | Purpose |
+| :--- | :--- |
+| `crm_account` | Companies and organizations |
+| `crm_contact` | People at an account |
+```
+
+In-repo reference: `examples/app-showcase/src/docs/showcase_docs_guide.md`.
+
+---
+
 ## CRM UI Blueprint (Metadata-First)
 
 Use this CRM-style structure as the canonical UI assembly reference: