fix(#2643): align skill frontmatter name with workflow gsd: emission (#2672)

Flat-skills installs write SKILL.md files under gsd-<cmd>/ dirs, but
Claude Code resolves skills by their frontmatter `name:`, not directory
name. PR #2595 normalized every `/gsd-<cmd>` to `/gsd:<cmd>` across
workflows — including inside `Skill(skill="...")` args — but the
installer still emitted `name: gsd-<cmd>`, so every Skill() call on a
flat-skills install resolved to nothing.

Fix: emit `name: gsd:<cmd>` (colon form) in
`convertClaudeCommandToClaudeSkill`. Keep the hyphen-form directory
name for Windows path safety.

Codex stays on hyphen form: its adapter invokes skills as `$gsd-<cmd>`
(shell-var syntax) and a colon would terminate the variable name.
`convertClaudeCommandToCodexSkill` uses `yamlQuote(skillName)` directly
and is untouched.

- Extract `skillFrontmatterName(dirName)` helper (exported for tests).
- Update claude-skills-migration and qwen-skills-migration assertions
  that encoded the old hyphen emission.
- Add `tests/bug-2643-skill-frontmatter-name.test.cjs` asserting every
  `Skill(skill="gsd:<cmd>")` reference in workflows resolves to an
  emitted frontmatter name.

Full suite: 5452/5452 passing.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

bin/install.js

@@ -1113,11 +1113,31 @@ function convertClaudeCommandToCopilotSkill(content, skillName, isGlobal = false
   return `${fm}\n${body}`;
 }
 
+/**
+ * Map a skill directory name (gsd-<cmd>) to the frontmatter `name:` used
+ * by Claude Code as the skill identity. Workflows emit `Skill(skill="gsd:<cmd>")`
+ * (colon form) and Claude Code resolves skills by frontmatter `name:`, not
+ * directory name — so emit colon form here. Directory stays hyphenated for
+ * Windows path safety. See #2643.
+ *
+ * Codex must NOT use this helper: its adapter invokes skills as `$gsd-<cmd>`
+ * (shell-var syntax) and a colon would terminate the variable name. Codex
+ * keeps the hyphen form via `yamlQuote(skillName)` directly.
+ */
+function skillFrontmatterName(skillDirName) {
+  if (typeof skillDirName !== 'string') return skillDirName;
+  // Idempotent on already-colon form.
+  if (skillDirName.includes(':')) return skillDirName;
+  // Only rewrite the first hyphen after the `gsd` prefix.
+  return skillDirName.replace(/^gsd-/, 'gsd:');
+}
+
 /**
  * Convert a Claude command (.md) to a Claude skill (SKILL.md).
  * Claude Code is the native format, so minimal conversion needed —
- * preserve allowed-tools as YAML multiline list, preserve argument-hint,
- * convert name from gsd:xxx to gsd-xxx format.
+ * preserve allowed-tools as YAML multiline list, preserve argument-hint.
+ * Emits `name: gsd:<cmd>` (colon) so Skill(skill="gsd:<cmd>") calls in
+ * workflows resolve on flat-skills installs — see #2643.
  */
 function convertClaudeCommandToClaudeSkill(content, skillName) {
   const { frontmatter, body } = extractFrontmatterAndBody(content);
@@ -1137,7 +1157,8 @@ function convertClaudeCommandToClaudeSkill(content, skillName) {
   }
 
   // Reconstruct frontmatter in Claude skill format
-  let fm = `---\nname: ${skillName}\ndescription: ${yamlQuote(description)}\n`;
+  const frontmatterName = skillFrontmatterName(skillName);
+  let fm = `---\nname: ${frontmatterName}\ndescription: ${yamlQuote(description)}\n`;
   if (argumentHint) fm += `argument-hint: ${yamlQuote(argumentHint)}\n`;
   if (agent) fm += `agent: ${agent}\n`;
   if (toolsBlock) fm += toolsBlock;
@@ -7265,6 +7286,7 @@ if (process.env.GSD_TEST_MODE) {
     convertClaudeAgentToAntigravityAgent,
     copyCommandsAsAntigravitySkills,
     convertClaudeCommandToClaudeSkill,
+    skillFrontmatterName,
     copyCommandsAsClaudeSkills,
     convertClaudeToWindsurfMarkdown,
     convertClaudeCommandToWindsurfSkill,