refactor(bin): move non-spec root files into references/ across four skills

grill-with-docs, improve-codebase-architecture, tdd, and triage kept
non-spec markdown files at their skill root, in violation of
skill-audit's file-structure.md rule (only SKILL.md/README.md belong
at the root; everything else lives in scripts/, references/, assets/
or tests/). A root-level file is invisible to the ADR-0020
dangling-reference gate, which only resolves unqualified
`references/...` pointers.

- Moved and renamed to lowercase-kebab-case under references/:
  grill-with-docs (ADR-FORMAT.md, CONTEXT-FORMAT.md),
  improve-codebase-architecture (DEEPENING.md, INTERFACE-DESIGN.md,
  LANGUAGE.md), tdd (five files, casing was already fine), triage
  (AGENT-BRIEF.md, OUT-OF-SCOPE.md).
- Updated every in-skill link to the new references/ paths, including
  link text that still showed the old uppercase filenames.
- Fixed improve-codebase-architecture/SKILL.md's cross-skill citation
  of grill-with-docs's two files to the sanctioned possessive form
  with the references/ segment included.
- Updated all four skills' README.md file tables to match.
- Regenerated the flat content mirror via
  scripts/sync-plugin-content.sh --all.

Fixes #122.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PDj6F7SPXzh3FtPN78dZ88

plugins/bin/.apm/skills/triage/SKILL.md

@@ -20,8 +20,8 @@ Every comment or issue posted to the issue tracker during triage **must** start
 
 ## Reference docs
 
-- [AGENT-BRIEF.md](AGENT-BRIEF.md) — how to write durable agent briefs
-- [OUT-OF-SCOPE.md](OUT-OF-SCOPE.md) — how the `.out-of-scope/` knowledge base works
+- [agent-brief.md](references/agent-brief.md) — how to write durable agent briefs
+- [out-of-scope.md](references/out-of-scope.md) — how the `.out-of-scope/` knowledge base works
 
 ## Roles
 
@@ -74,11 +74,11 @@ Show counts and a one-line summary per issue. Let the maintainer pick.
 4. **Grill (if needed).** If the issue needs fleshing out, run a `/grill-with-docs` session.
 
 5. **Apply the outcome:**
-   - `ready-for-agent` — post an agent brief comment ([AGENT-BRIEF.md](AGENT-BRIEF.md)).
+   - `ready-for-agent` — post an agent brief comment ([agent-brief.md](references/agent-brief.md)).
    - `ready-for-human` — same structure as an agent brief, but note why it can't be delegated (judgment calls, external access, design decisions, manual testing).
    - `needs-info` — post triage notes (template below).
    - `wontfix` (bug) — polite explanation, then close.
-   - `wontfix` (enhancement) — write to `.out-of-scope/`, link to it from a comment, then close ([OUT-OF-SCOPE.md](OUT-OF-SCOPE.md)).
+   - `wontfix` (enhancement) — write to `.out-of-scope/`, link to it from a comment, then close ([out-of-scope.md](references/out-of-scope.md)).
    - `needs-triage` — apply the role. Optional comment if there's partial progress.
 
 ## Quick state override