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>

src/runtime-artifact-layout.cts

@@ -350,11 +350,21 @@ function resolveRuntimeArtifactLayout(runtime: string, configDir: string, scope:
       break;
 
     case 'opencode':
-      kinds = [commandsKind('command', 'gsd-', configDir)];
+      // OpenCode reads flat slash commands from command/ and on-demand skills
+      // from skills/<name>/SKILL.md (https://opencode.ai/docs/skills). Emit both.
+      kinds = [
+        commandsKind('command', 'gsd-', configDir),
+        skillsKind('skills', 'gsd-', 'convertClaudeCommandToOpencodeSkill', 'opencode', configDir),
+      ];
       break;
 
     case 'kilo':
-      kinds = [commandsKind('command', 'gsd-', configDir)];
+      // Kilo derives from OpenCode and shares the skills/<name>/SKILL.md layout
+      // (https://kilo.ai/docs/customize/skills). Emit flat commands + skills.
+      kinds = [
+        commandsKind('command', 'gsd-', configDir),
+        skillsKind('skills', 'gsd-', 'convertClaudeCommandToKiloSkill', 'kilo', configDir),
+      ];
       break;
 
     default: