fix(#2957): claude+global post-install instructs restart and skill fallback (#2960)

* fix(#2957): claude+global post-install instructs restart and skill fallback

`npx get-shit-done-cc --claude --global` writes skills to
`~/.claude/skills/gsd-*/SKILL.md` (CC 2.1.88+ format) and removes the
legacy `~/.claude/commands/gsd/`. The post-install message still told
users to type `/gsd-new-project` without mentioning the required Claude
Code restart or the skill-name fallback. On configurations where CC
does not auto-surface skills in the slash menu, users hit "no commands
appear" and assumed the install failed.

Split the post-install message: the existing single-line instruction
stays for every non-Claude runtime and for `--claude --local`. For
`--claude --global` it now reads:

  Restart Claude Code, then in any directory either type
  /gsd-new-project or ask Claude to run the gsd-new-project skill.

This covers both invocation paths and surfaces the restart requirement.

Add tests/bug-2957-claude-global-postinstall-message.test.cjs as a
regression guard: captures the printed message for claude+global,
claude+local, and opencode+global; asserts content for each. Verified
the test fails on main (pre-fix) and passes after the fix.

Closes #2957

* test(#2957): assert legacy generic instruction is replaced not extended

CodeRabbit flagged that the test would still pass if the new restart/
fallback copy were printed *alongside* the old 'open a blank directory'
instruction. Adding a doesNotMatch assertion proves the claude+global
branch replaces the legacy line rather than appending to it.

bin/install.js

@@ -8150,6 +8150,20 @@ function finishInstall(settingsPath, settings, statuslineCommand, shouldInstallS
   if (runtime === 'cline') command = '/gsd-new-project';
   if (runtime === 'qwen') command = '/gsd-new-project';
   if (runtime === 'hermes') command = '/gsd-new-project';
+
+  // Claude Code global installs use the skills/ format (CC 2.1.88+).
+  // Restart is required for CC to pick up newly-installed skills, and the
+  // slash-menu surface depends on CC version — so the instruction needs to
+  // cover both invocation paths to avoid #2957-style "no commands appear".
+  if (runtime === 'claude' && isGlobal) {
+    console.log(`
+  ${green}Done!${reset} Restart ${program}, then in any directory either type ${cyan}${command}${reset} or ask Claude to run the ${cyan}gsd-new-project${reset} skill.
+
+  ${cyan}Join the community:${reset} https://discord.gg/mYgfVNfA2r
+`);
+    return;
+  }
+
   console.log(`
   ${green}Done!${reset} Open a blank directory in ${program} and run ${cyan}${command}${reset}.