Add PROSE adapter layer (v0.2.0): constructors, renderers, body sections

- Move prose.typ to src/adapters/prose.typ (filesystem boundary visible)
- Add p-agent, p-instruction, p-skill, p-workflow constructors
- Add render-agent, render-instruction, render-skill, render-workflow
- Extend p-instruction sections: body (raw Markdown) as alternative to items
- Promote md-table, md-row, escape-pipes to public API
- Add PROSE ingest support (agent, instruction, skill, workflow TOML keys)
- Add test-prose.typ with 8 test groups + TOML fixtures
- Update Boundary.md with adapter layer documentation

Author: blessuselessk

Boundary.md

@@ -27,6 +27,7 @@ rules apply to consumers building layers on top of this package.
 │  lib.typ → src/primitives.typ       │
 │          → src/render.typ           │
 │          → src/validate.typ         │
+│          → src/adapters/prose.typ   │
 └─────────────────────────────────────┘
 ```
 
@@ -122,9 +123,47 @@ must use its own tagging convention in a separate namespace.
 
 ---
 
+## Markdown Utilities (promoted in v0.2.0)
+
+Previously internal `_md-*` helpers, now public for use by adapter layers
+and consumers building custom renderers.
+
+| Symbol | Input | Returns |
+|--------|-------|---------|
+| `md-table` | `headers`, `rows` | Markdown table string |
+| `md-row` | `cells` | Single Markdown table row string |
+| `escape-pipes` | `string` | String with `\|` escaped |
+
+These are stable utilities. Their signatures are fixed from v0.2.0.
+
+---
+
+## Adapter Layer (Phase 3, evolving)
+
+PROSE primitive constructors and renderers. These are NOT under the
+immutable 10-symbol contract. Signatures may change between minor versions.
+
+| Symbol | Type | Stable |
+|--------|------|--------|
+| `p-agent` | constructor | no (adapter, evolving) |
+| `p-instruction` | constructor | no (adapter, evolving) |
+| `p-skill` | constructor | no (adapter, evolving) |
+| `p-workflow` | constructor | no (adapter, evolving) |
+| `render-agent` | renderer | no (adapter, evolving) |
+| `render-instruction` | renderer | no (adapter, evolving) |
+| `render-skill` | renderer | no (adapter, evolving) |
+| `render-workflow` | renderer | no (adapter, evolving) |
+
+Adapter-layer dictionaries carry `_type` tags (`"agent"`, `"instruction"`,
+`"skill"`, `"workflow"`). The same `_type` rules apply: consumers must not
+read or branch on `_type` — that is the render layer's responsibility.
+
+---
+
 ## Versioning Rule
 
 The public API (10 symbols, their signatures, and their Markdown output
 contract) is stable within a major version. Any change to the Markdown
 output format — even whitespace — is a breaking change and requires a
 major version bump. The internal symbols carry no versioning guarantee.
+Adapter layer symbols follow semver but are not under the immutable contract.

lib.typ

@@ -33,8 +33,20 @@
 //   field          builds a schema field dict
 //   entry          builds a context entry dict
 //   checkpoint     shorthand for p-checkpoint (positional args)
+//
+// Markdown utilities (promoted from internal in v0.2.0):
+//   md-table       headers, rows → Markdown table string
+//   md-row         cells → single Markdown table row
+//   escape-pipes   string → string with | escaped
+//
+// PROSE adapter layer (Phase 3, evolving — NOT under 10-symbol contract):
+//   p-agent, p-instruction, p-skill, p-workflow     constructors
+//   render-agent, render-instruction, render-skill, render-workflow  renderers
 
 #import "src/primitives.typ": p-context, p-schema, p-checkpoint, p-chat-mode, p-prompt
 #import "src/render.typ":     render-context, render-schema, render-checkpoint, render-chat-mode, render-prompt
+#import "src/render.typ":     md-table, md-row, escape-pipes
+#import "src/adapters/prose.typ": p-agent, p-instruction, p-skill, p-workflow
+#import "src/adapters/prose.typ": render-agent, render-instruction, render-skill, render-workflow
 #import "src/ingest.typ":     from-toml, from-yaml
 #import "src/helpers.typ":    ctx, schema, field, entry, checkpoint