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.

CHANGELOG.md

@@ -10,6 +10,7 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 - **`gsd-sdk query agent-skills` emits raw `<agent_skills>` block instead of JSON-wrapped string** — workflows that embed via `$(gsd-sdk query agent-skills <agent>)` were receiving a JSON-quoted string literal mid-prompt (e.g. `"<agent_skills>\n…"`), silently breaking all `<agent_skills>` injection into spawned subagents. The CLI dispatcher now honors an opt-in `format: 'text'` field on `QueryResult` and writes such results raw via `process.stdout.write`; `--pick` always returns JSON regardless. (#2917)
 - **`sketch --wrap-up` now dispatches correctly** — `/gsd-sketch --wrap-up` was silently no-oping because the flag dispatch wiring was omitted when the micro-skill entry point was absorbed in #2790. (#2949)
+- **Post-install message for `--claude --global` now reflects the skills-only layout** — `npx get-shit-done-cc --claude --global` ships skills to `~/.claude/skills/gsd-*/SKILL.md` (CC 2.1.88+ format) and removes the legacy `commands/gsd/`, but the post-install message still instructed users to type `/gsd-new-project` without mentioning the required CC restart or the skill-name fallback. Users on configurations where CC does not auto-surface skills in the slash menu hit a dead-end "no commands appear". The Claude-global branch now reads: *"Restart Claude Code, then in any directory either type /gsd-new-project or ask Claude to run the gsd-new-project skill."* Other runtimes and the `--claude --local` path are unchanged. (#2957)
 
 ### Added — 1.40.0-rc.1
 - **Six namespace meta-skills with keyword-tag descriptions** — replace the flat 86-skill