fix: pair-agent skill compliance + fix all 16 pre-existing test failures

Root cause: pair-agent was added without completing the gen-skill-docs
compliance checklist. All 16 failures traced back to this.

Fixes:
- Sync package.json version to VERSION (0.15.9.0)
- Add "(gstack)" to pair-agent description for discoverability
- Add pair-agent to Codex path exception (legitimately documents ~/.codex/)
- Add CLI_COMMANDS (status, pair-agent, tunnel) to skill parser allowlist
- Regenerate SKILL.md for all hosts (claude, codex, factory, kiro, etc.)
- Update golden file baselines for ship skill
- Fix relink tests: pass GSTACK_INSTALL_DIR to auto-relink calls so they
  use the fast mock install instead of scanning real ~/.claude/skills/gstack

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/helpers/skill-parser.ts

@@ -15,6 +15,11 @@ import { parseSnapshotArgs } from '../../browse/src/snapshot';
 import * as fs from 'fs';
 import * as path from 'path';
 
+/** CLI-only commands: valid $B invocations that are handled by the CLI, not the server */
+const CLI_COMMANDS = new Set([
+  'status', 'pair-agent', 'tunnel',
+]);
+
 export interface BrowseCommand {
   command: string;
   args: string[];
@@ -112,7 +117,7 @@ export function validateSkill(skillPath: string): ValidationResult {
   }
 
   for (const cmd of commands) {
-    if (!ALL_COMMANDS.has(cmd.command)) {
+    if (!ALL_COMMANDS.has(cmd.command) && !CLI_COMMANDS.has(cmd.command)) {
       result.invalid.push(cmd);
       continue;
     }