fix(mcp): rule-docs embed + windows-11-arm runner

[aram-devdocs]

Summary

Two more fixes blocking the v0.0.5 release pipeline (after #248, #251, #253, #255, #257).

1. `include_str!` outside crate breaks cargo publish

`plumb-mcp/src/explain.rs` did `include_str!("../../../docs/src/rules/.md")`. `cargo publish` doesn't traverse outside the crate dir, so the v0.0.5 publish died with:

```
error: couldn't read `src/../../../docs/src/rules/a11y-touch-target.md`:
No such file or directory (os error 2)
```

(release-please.yml run 25488993683.)

Fix: move all 16 rule-doc files to `crates/plumb-mcp/rule-docs/` (canonical), and replace the old location with relative symlinks so mdBook still resolves them under `docs/src/rules/.md`. `include_str!` paths now resolve to a sibling directory inside the crate.

2. aarch64-pc-windows-msvc cross-compile fails

cargo-dist scheduled the ARM64 Windows build on a x86_64 `windows-latest` runner, which lacks the ARM64 cross-compile toolchain:

```
help: no idea how to cross-compile from x86_64-pc-windows-msvc
to windows with architecture aarch64
```

(release.yml run 25489026809.)

Fix: switch to native `windows-11-arm` runner.

Verified

• `cargo nextest run -p plumb-mcp` ✅ 30/30
• `cargo xtask sync-rules-index` ✅ "16 built-in rule(s); all have docs pages"
• `mdbook build docs/` ✅

🤖 Generated with Claude Code

[github-actions]

I have enough context for a complete review. Here is the full assessment.

---

PR 259: fix(release): rule-docs embed + windows-11-arm runner

Scope

Bucket	Files
plumb-mcp	src/explain.rs, rule-docs/*.md (×16)
docs	docs/src/rules/*.md (×16, converted to symlinks)
ci	.github/workflows/release.yml (+1/-1)

---

1. Determinism — PASS

RULE_DOCS is a const slice. Sorted alphabetically by rule_id; verified: a11y < baseline < color < edge < opacity < radius < shadow < sibling < spacing < type < z. No wall-clock. No HashMap in any output path. No env reads. All good.

2. Workspace layering — PASS

Change is entirely within plumb-mcp and docs. No new crate dependencies. #![forbid(unsafe_code)] is untouched. No println!/eprintln! introduced.

3. Error handling — PASS

lookup() returns Option<&'static RuleDoc> — callers map None to a JSON-RPC error as required. No unwrap/expect in new code.

4. Test coverage — PASS

include_str! paths are verified at compile time — a wrong path is a compile error, not a runtime regression. The existing every_builtin_rule_has_doc_entry test in mcp_protocol.rs guards table-vs-engine drift. All 16 rule-docs are present in crates/plumb-mcp/rule-docs/ and all 16 include_str! entries in explain.rs map to real files.

5. Documentation accuracy — ISSUES

crates/plumb-mcp/src/explain.rs:5 and :26 — both the module-level doc and the RuleDoc.markdown field doc still name the old path:

markdown body of `docs/src/rules/<slug>.md`

The canonical source is now crates/plumb-mcp/rule-docs/<slug>.md. docs/src/rules/*.md are symlinks, not source files. The comments are stale.

crates/plumb-mcp/CLAUDE.md:59 — the anti-patterns section reads:

Embedding rule docs verbatim in explain_rule. Read from docs/src/rules/<slug>.md so the book and the MCP response stay in sync.

This is now exactly backwards. The PR intentionally moves to include_str!-from-within-the-crate because reading from docs/src/rules/<slug>.md at publish time is what broke cargo publish. Any future agent reading this CLAUDE.md will conclude the current explain.rs implementation is an anti-pattern and attempt to revert it. This is the highest-impact stale doc in the diff — CLAUDE.md is consumed by every AI session on this repo.

Required fixes:

• crates/plumb-mcp/src/explain.rs:5,26 — update path reference from docs/src/rules/<slug>.md → rule-docs/<slug>.md.
• crates/plumb-mcp/CLAUDE.md:59 — replace the anti-pattern entry. The new canonical pattern is: canonical source lives in crates/plumb-mcp/rule-docs/<slug>.md, embedded at compile time via include_str!; docs/src/rules/ symlinks keep mdBook in sync. The anti-pattern is referencing a path outside the crate root in include_str!.

6. CI change — PASS

windows-11-arm is the correct native runner for aarch64-pc-windows-msvc. The x86-64 windows-latest runner has no ARM64 cross-compile toolchain; this fix is precise and minimal.

---

Punch list

File	Line	Severity	Issue
crates/plumb-mcp/CLAUDE.md	59	Warning	Anti-pattern entry is inverted after this PR; future agents will misread the current implementation as wrong
crates/plumb-mcp/src/explain.rs	5	Nit	Module doc references stale path docs/src/rules/<slug>.md
crates/plumb-mcp/src/explain.rs	26	Nit	RuleDoc.markdown field doc references stale path docs/src/rules/<slug>.md

The CLAUDE.md item is the only one that could cause active harm (misleads AI agents running in future sessions). The explain.rs nits are cosmetic.

Verdict: REQUEST_CHANGES