Add pull-request vocabulary to git-workflow-and-versioning description

The skill body already covers pull requests -- "ideally a separate PR" and
"Target ~100 lines per commit/PR" -- but the frontmatter description never
uses the words "pull request" or "PR". Prompts phrased that way therefore
do not route to this skill first.

Adds a trigger case for the gap, and the vocabulary that closes it.

Tier-2 routing, via scripts/run-evals.js:

  baseline                      86%  67/78
  with new case, no fix         85%  67/79   <- case does not rank first
  with new case and fix         86%  68/79   <- case ranks first

Exactly one case changed rank; no other skill regressed.
scripts/validate-skills.js passes: 24 skills, 0 errors, 0 warnings.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

evals/cases/git-workflow-and-versioning.json

@@ -13,6 +13,10 @@
       {
         "prompt": "How should we tag and version this release?",
         "top_k": 3
+      },
+      {
+        "prompt": "Commit this work and open a pull request",
+        "top_k": 3
       }
     ],
     "negative": [

skills/git-workflow-and-versioning/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: git-workflow-and-versioning
-description: Structures git workflow practices. Use when making any code change. Use when committing, branching, resolving conflicts, or when you need to organize work across multiple parallel streams. Use when cutting a release, choosing a semantic version bump, tagging, or writing a changelog.
+description: Structures git workflow practices. Use when making any code change. Use when committing, branching, resolving conflicts, opening or reviewing a pull request (PR), pushing to a remote, or when you need to organize work across multiple parallel streams. Use when cutting a release, choosing a semantic version bump, tagging, or writing a changelog.
 ---
 
 # Git Workflow and Versioning