enh(#784): emit native skills for OpenCode + Kilo runtimes (#810)

* feat(#784): emit native skills for OpenCode + Kilo runtimes

OpenCode and Kilo share a config schema and both discover on-demand
skills from skills/<name>/SKILL.md. The installer previously emitted
only flat commands (command/) and file-based agents (agents/) for these
runtimes. Add a shared OpenCode-family skill writer that stages each GSD
command as a spec-compliant SKILL.md (name matching the directory,
description 1-1024 chars), wired through the runtime artifact layout so
uninstall cleans skills/ automatically. Skills respect the active
install profile.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(#784): correct skill body paths + preserve user dev-preferences

Address adversarial-review findings:
- Add opencode/kilo cases to _applyRuntimeRewrites so staged SKILL.md
  bodies are re-pointed from the converter's hardcoded default config dir
  to the actual install target (fixes --local / --config-dir installs;
  commands/agents already did this by applying pathPrefix pre-conversion).
- Preserve user-owned skills/gsd-dev-preferences across reinstall in
  installOpencodeFamilySkills (snapshot+restore around the gsd-* prune),
  matching installRuntimeArtifacts.
- Export installOpencodeFamilySkills and add regression tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(#784): guarantee command/skill body parity, fix kilo-alt double-rewrite

Follow-up adversarial-review found the post-conversion path rewrite could
double-rewrite custom Kilo dirs (kilo -> kilo-alt -> kilo-alt-alt) because
the kilo pathPrefix is a $HOME (non-absolute) superset of the hardcoded
default base. Restructure so OpenCode/Kilo skills mirror copyFlattenedCommands
exactly: stage raw commands, apply pathPrefix BEFORE conversion via a new
shared applyOpencodeFamilyPathPrefix() helper (now used by both the command
and skill writers), then convert. This guarantees byte-for-byte command/
skill body parity for global, --local, and --config-dir installs and removes
the prefix-overlap hazard. Drop the fragile _applyRuntimeRewrites opencode/
kilo case. Strengthen the path regression test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* refactor(#784): derive opencode/kilo skills from the same staged command set

Pass the installer's _stageSkills() output directly to
installOpencodeFamilySkills instead of re-staging via the layout, so the
command/ and skills/ surfaces always cover the identical profile-resolved
set — including the --minimal/--core-only alias path, which stages
differently from a plain --profile=core. Verified: minimal install now
emits 8 commands and 8 skills.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#784): set changeset PR number to 810

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(#784): fully escape backslashes in test helper (CodeQL js/incomplete-string-escaping)

Replace the dot-only escape `replace(/[.]/g, '\\.')` with a complete
regex-escape pattern `replace(/[\\.*+?^${}()|[\]]/g, '\\$&')` so all
regex metacharacters (including backslash itself) in `defaultBase` are
safely escaped before interpolation into `new RegExp(...)`.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/runtime-converters.test.cjs

@@ -18,6 +18,8 @@ const {
   convertClaudeToOpencodeFrontmatter,
   convertClaudeToKiloFrontmatter,
   convertClaudeToGeminiAgent,
+  convertClaudeCommandToOpencodeSkill,
+  convertClaudeCommandToKiloSkill,
   neutralizeAgentReferences,
 } = require('../bin/install.js');
 
@@ -344,3 +346,70 @@ describe('neutralizeAgentReferences', () => {
     assert.ok(result.includes('claude-code'), 'claude-code preserved');
   });
 });
+
+// ─── OpenCode-family skill converters (SKILL.md) — #784 ──────────────────────
+
+const SKILL_SAMPLE_COMMAND = `---
+description: Show available GSD commands and usage guide
+argument-hint: "[topic]"
+allowed-tools:
+  - Read
+  - Bash
+---
+
+Run \`/gsd:help\` to see the guide. AskUserQuestion when unsure.
+`;
+
+const SKILL_BETA_COMMAND = `---
+description: "[BETA] Offload plan phase to the cloud and import back."
+---
+
+Body for /gsd:ultraplan-phase.
+`;
+
+describe('convertClaudeCommandToOpencodeSkill / convertClaudeCommandToKiloSkill (#784)', () => {
+  const cases = [
+    { label: 'opencode', convert: convertClaudeCommandToOpencodeSkill },
+    { label: 'kilo', convert: convertClaudeCommandToKiloSkill },
+  ];
+
+  for (const { label, convert } of cases) {
+    describe(`${label} skill conversion`, () => {
+      test('emits SKILL.md frontmatter with name matching the skill dir', () => {
+        const out = convert(SKILL_SAMPLE_COMMAND, 'gsd-help');
+        assert.ok(out.startsWith('---\n'), 'opens with frontmatter');
+        assert.match(out, /^name: gsd-help$/m, 'name equals the skill name');
+      });
+
+      test('preserves the description from the source command', () => {
+        const out = convert(SKILL_SAMPLE_COMMAND, 'gsd-help');
+        assert.match(out, /^description: "Show available GSD commands and usage guide"$/m);
+      });
+
+      test('drops the command tools/permission block (skills inherit perms)', () => {
+        const out = convert(SKILL_SAMPLE_COMMAND, 'gsd-help');
+        const fmEnd = out.indexOf('\n---', 4);
+        const fm = out.slice(0, fmEnd);
+        assert.ok(!/tools:/.test(fm), 'no tools block in skill frontmatter');
+        assert.ok(!/permission:/.test(fm), 'no permission block in skill frontmatter');
+      });
+
+      test('rewrites /gsd: colon refs to hyphen form in the body', () => {
+        const out = convert(SKILL_SAMPLE_COMMAND, 'gsd-help');
+        assert.ok(!/\/gsd:/.test(out), 'no /gsd: colon refs remain');
+        assert.match(out, /\/gsd-help/, 'colon ref rewritten to hyphen form');
+      });
+
+      test('quotes descriptions with leading YAML flow indicators ([BETA])', () => {
+        const out = convert(SKILL_BETA_COMMAND, 'gsd-ultraplan-phase');
+        assert.match(out, /^description: "\[BETA\] /m, 'leading [BETA] safely quoted');
+      });
+
+      test('falls back to a synthetic description when none present', () => {
+        const out = convert('Body only, no frontmatter.', 'gsd-mystery');
+        assert.match(out, /^name: gsd-mystery$/m);
+        assert.match(out, /^description: "Run GSD workflow gsd-mystery\."$/m);
+      });
+    });
+  }
+});