Migrate shared skills to `ai.skillz` symlinks

Drop inline `commit-msg/SKILL.md` — now deployed
as a symlink from the central `ai.skillz` repo via
`deploy-skill.sh`.

Gitignore all symlinked skill dirs so they stay
machine-local:
- fully-symlinked: `py-codestyle`, `close-wkt`,
  `open-wkt`, `plan-io`, `prompt-io`,
  `code-review-changes`, `resolve-conflicts`,
  `inter-skill-review`, `yt-url-lookup`
- hybrid (symlinked SKILL.md + references):
  `commit-msg/SKILL.md`, `pr-msg/SKILL.md`,
  `pr-msg/references`

(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

.claude/skills/commit-msg/SKILL.md

@@ -1,86 +0,0 @@
----
-name: commit-msg
-description: >
-  Generate git commit messages following project style. Use when user
-  wants to create a commit or asks for a commit message.
-argument-hint: "[optional-scope-or-description]"
-disable-model-invocation: true
-allowed-tools:
-  - Bash(git *)
-  - Bash(date *)
-  - Bash(cp *)
-  - Read
-  - Grep
-  - Glob
-  - Write
----
-
-When generating commit messages, always follow this process:
-
-0. **Check for staged changes**: if `git diff --staged` is
-   empty, STOP and tell the user "nothing is staged!" with
-   a reminder to `git add` before invoking this skill.
-
-1. **Gather context** from the staged diff and recent
-   history:
-
-   - Staged changes: !`git diff --staged --stat`
-   - Recent commits: !`git log --oneline -5`
-
-2. **Analyze the diff**: understand what files changed and
-   the nature of the changes (new feature, bug fix, refactor,
-   etc.)
-
-3. **Write the commit message** following these rules:
-
-**Use the accompanying style guide:**
-- See [style-guide-reference.md](style-guide-reference.md)
-  for detailed analysis of past commits in this repo.
-
-**Subject Line Format:**
-- Present tense verbs: Add, Drop, Fix, Use, Move, Adjust, etc.
-- Target 50 chars (hard max: 67)
-- Backticks around ALL code elements (classes, functions, modules, vars)
-- Specific about what changed
-
-**Body Format (optional - keep simple if warranted):**
-- Max 67 char line length
-- Use `-` bullets for lists
-- Section markers: `Also,` `Deats,` `Other,` `Further,`
-- Abbreviations: msg, bg, ctx, impl, mod, obvi, tn, fn, bc, var, prolly
-- Casual yet technically precise tone
-- Never write lines with only whitespace
-
-**Common Opening Patterns:**
-- New features: "Add `feature` to `module`"
-- Removals: "Drop `attr` from `class`"
-- Bug fixes: "Fix `issue` in `function`"
-- Code moves: "Move `thing` to `new_location`"
-- Adoption: "Use `new_tool` for `task`"
-- Minor tweaks: "Adjust `behavior` in `component`"
-
-4. **Write to TWO files**:
-   - `.claude/<timestamp>_<hash>_commit_msg.md`
-     * with `<timestamp>` from `date -u +%Y%m%dT%H%M%SZ` or similar
-       filesystem-safe format.
-     * and `<hash>` from `git log -1 --format=%h` first 7 chars.
-   - `.claude/git_commit_msg_LATEST.md` (overwrite)
-
-5. **Always include credit footer**:
-
-When no part of the patch was written by `claude`,
-```
-(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
-[claude-code-gh]: https://github.com/anthropics/claude-code
-```
-
-when some or all of the patch was written by `claude`
-instead use,
-
-```
-(this patch was generated in some part by [`claude-code`][claude-code-gh])
-[claude-code-gh]: https://github.com/anthropics/claude-code
-```
-
-Keep it concise. Match the tone of recent commits. For simple
-changes, use subject line only.

.gitignore

@@ -125,6 +125,22 @@ venv.bak/
 # per-skill session/conf (machine-local)
 .claude/skills/*/conf.toml
 
+# ai.skillz symlinks (machine-local, deploy via deploy-skill.sh)
+.claude/skills/py-codestyle
+.claude/skills/code-review-changes
+.claude/skills/close-wkt
+.claude/skills/open-wkt
+.claude/skills/plan-io
+.claude/skills/prompt-io
+.claude/skills/resolve-conflicts
+.claude/skills/inter-skill-review
+.claude/skills/yt-url-lookup
+
+# hybrid skills — symlinked SKILL.md + references
+.claude/skills/commit-msg/SKILL.md
+.claude/skills/pr-msg/SKILL.md
+.claude/skills/pr-msg/references
+
 # nix develop --profile .nixdev
 .nixdev*