chore(skills): tldraw-migrate sources release notes from github (tldraw#8779)

In order to keep the tldraw-migrate skill's release-notes view aligned
with what's actually on `main`, this PR switches the changelog source
from `tldraw.dev/llms-releases.txt` to GitHub's
`apps/docs/content/releases/` directory. A few smaller improvements ride
along to make the skill easier to distribute across agents.

Previously the skill `curl`'d the published `llms-releases.txt` from
tldraw.dev, which meant pre-release notes (`next.mdx`) and recently
merged but unpublished release-note edits were invisible to the
migration workflow. The skill now lists `apps/docs/content/releases/`
via the GitHub contents API and fetches each `.mdx` directly from
`raw.githubusercontent.com`. GitHub is the source of truth.

Other changes:

- Pre-release semver suffixes (e.g. `4.7.0-canary.abc`) are now
preserved in `detect-versions.mjs` and compared correctly in the new
fetcher, so a user on a canary gets the right version range and the
upcoming `next.mdx` content.
- The `${SKILL_DIR}` probe gained `.codex/skills/`.
- Removed `disable-model-invocation: true` from the frontmatter so any
agent that respects skill metadata can auto-invoke after copying.
- Added a one-line cross-agent note above the auto-fetch blocks for
agents that don't auto-run Claude Code's `!`-prefix syntax (Cursor,
Codex, plain Claude API, etc.).
- Replaced `filter-changelog.mjs` with `fetch-release-notes.mjs`
(filtering happens at fetch time).

The motivation is partly to support distributing the skill via a
one-shot prompt — "copy `skills/tldraw-migrate` from this repo into your
repo and follow it" — across different coding agents.

### Change type

- [x] `improvement`

### Test plan

1. From a project on tldraw 4.4.0, run `/tldraw-migrate` — should fetch
v4.5.0 notes from GitHub and skip `next.mdx` (stable target).
2. From a project on a pre-release like `4.7.0-canary.abc` with target
`canary`, run `/tldraw-migrate` — should fetch `next.mdx` into
`references/tldraw-next.mdx`.
3. Pin a stable upper bound: `node
skills/tldraw-migrate/fetch-release-notes.mjs 4.0.0 4.2.0` — should
include v4.1.0 and v4.2.0 only.
4. Place the skill folder under each of `.claude/skills/`,
`.agents/skills/`, `.codex/skills/`, `.cursor/skills/`, `skills/` —
auto-fetch blocks resolve `SKILL_DIR` correctly in each case.

Author: steveruizok

skills/tldraw-migrate/README.md

@@ -0,0 +1,82 @@
+# tldraw-migrate skill
+
+> Note: Are you human? You should probably not be. Pass a link to this file to your agent of choice and have them take it from here.
+
+A portable agent skill that walks an AI coding agent through upgrading a project to a newer version of the tldraw SDK.
+
+This README documents distribution and installation. The skill itself lives in [`SKILL.md`](./SKILL.md).
+
+## Distribution
+
+The canonical source of truth is `skills/tldraw-migrate/` on `main` in the [tldraw monorepo](https://github.com/tldraw/tldraw). Distribute the skill by copying the entire folder into the agent-skills directory of the project being migrated. The skill is self-contained — `SKILL.md`, the three `.mjs` helpers, and a `references/` cache.
+
+### Where to install
+
+Copy `skills/tldraw-migrate/` into one of the following paths in the target project. The skill probes them in this order and uses the first one it finds:
+
+| Path | Harness |
+| --- | --- |
+| `.claude/skills/tldraw-migrate/` | Claude Code |
+| `.agents/skills/tldraw-migrate/` | Generic / open agent-skills spec |
+| `.codex/skills/tldraw-migrate/` | OpenAI Codex |
+| `.cursor/skills/tldraw-migrate/` | Cursor |
+| `skills/tldraw-migrate/` | Fallback / vendored alongside source |
+
+If multiple harnesses share a project, install once and symlink the others to the same folder (this is what the tldraw monorepo itself does — see `AGENTS.md`).
+
+### One-shot install from GitHub
+
+```sh
+DEST=.claude/skills/tldraw-migrate   # or .agents/skills/tldraw-migrate, .cursor/skills/tldraw-migrate, etc.
+mkdir -p "$DEST"
+curl -fsSL https://github.com/tldraw/tldraw/archive/refs/heads/main.tar.gz \
+  | tar -xz --strip-components=3 -C "$DEST" tldraw-main/skills/tldraw-migrate
+```
+
+### Updating an installed copy
+
+The skill changes whenever migration patterns shift in the SDK (new error categories, new helpers, edge-case fixes). Re-run the one-shot install command above to overwrite `SKILL.md` and the helper scripts, or pull the latest from `tldraw/tldraw` main. The skill's *content* — release notes and docs — is auto-refreshed on every invocation, so updating `SKILL.md` itself is only needed when the workflow changes.
+
+### Skill-location override
+
+If the skill is installed somewhere outside the probed locations, export `SKILL_DIR` before invocation:
+
+```sh
+SKILL_DIR=/abs/path/to/tldraw-migrate
+```
+
+The auto-fetch blocks and all internal grep examples honor this variable.
+
+## Requirements
+
+- **Node ≥ 20** for the three helper scripts (`detect-versions.mjs`, `detect-target.mjs`, `fetch-release-notes.mjs`). No npm dependencies — they are zero-dep ES modules.
+- **`curl`** for the docs fetch.
+- **`git`** is optional but improves from-version detection (the skill compares `main`, `HEAD~1`, and the working tree).
+- **`GITHUB_TOKEN`** env var is optional; setting it raises the unauthenticated GitHub API rate limit (60/hr) so re-runs and long version ranges don't fail.
+
+## What gets fetched on invocation
+
+The skill writes three files into `references/` at run time. None of them is committed to the skill's source — they are recreated on demand.
+
+| File | Source | When fetched |
+| --- | --- | --- |
+| `tldraw-releases.txt` | `github.com/tldraw/tldraw` → `apps/docs/content/releases/v*.mdx`, filtered to versions strictly greater than the detected from-version | Always |
+| `tldraw-full-docs.txt` | `tldraw.dev/llms-full.txt` | Cached locally, 30-day TTL — delete the file or wait 30 days to refresh |
+| `tldraw-next.mdx` | `github.com/tldraw/tldraw` → `apps/docs/content/releases/next.mdx` | Pre-release targets only (`canary`, `next`, `beta`, or pre-release semver) |
+
+GitHub is the source of truth, deliberately. `next.mdx` does not exist on npm, and tldraw.dev can lag behind main. This means migration recipes for unreleased versions are available to the skill the moment they land in `main`.
+
+## Harness compatibility
+
+The `!`-prefix bash blocks at the top of `SKILL.md` are written for Claude Code's auto-execute syntax. Other harnesses (Cursor, Codex, plain Claude API, etc.) must run each block as a shell command before continuing the workflow. The skill flags this explicitly at the top of the resources section.
+
+For agent harnesses without slash-command support, the skill still works as a plain workflow document — point the agent at `SKILL.md` and the same step-by-step process applies.
+
+## Files in this folder
+
+- `SKILL.md` — the skill workflow itself
+- `detect-versions.mjs` — resolves the from-version (explicit arg → `main` → `HEAD~1` → working tree)
+- `detect-target.mjs` — resolves the target version (default `latest`; accepts a dist-tag or semver)
+- `fetch-release-notes.mjs` — pulls release notes between two versions from `tldraw/tldraw` main
+- `references/` — auto-populated cache of fetched references (gitignored or freshly recreated)
+- `README.md` — this file