fix(#891): probe non-Claude runtime homes in gsd-tools launcher shim detection (#911)

- Updated `gsd-core/workflows/_runtime-launcher.snippet.sh` with 15 new
  `elif` arms covering Hermes, Cursor, Codex, Gemini, Copilot, Windsurf,
  Augment, Trae, Qwen, CodeBuddy, Cline, Grok, Antigravity, OpenCode, and
  Kilo (respecting each runtime's env-var override with a `$HOME`-relative
  default).
- Re-ran `scripts/sync-runtime-launcher.cjs` to propagate the expanded
  snippet into all `gsd-core/workflows/*.md` files (~70 files).
- Manually applied the same snippet update to `commands/gsd/import.md`
  (1 occurrence) and `commands/gsd/graphify.md` (5 occurrences) — these
  are not covered by the sync script.
- Updated `tests/workflow-size-budget.test.cjs` budgets (XL/LARGE/DEFAULT
  + discuss-phase target) to account for the ~3 KB snippet expansion.
- Added regression test `tests/bug-891-non-claude-runtime-home-fallback.test.cjs`
  (6 tests: structural probe presence, ordering, behavioral HERMES_HOME
  env-var + default-path stubs, resolution order, and workflow propagation).
- Added `.changeset/891-launcher-non-claude-runtime-homes.md` (Fixed).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
(cherry picked from commit a90c654745)

.changeset/891-launcher-non-claude-runtime-homes.md

@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 903
+---
+**`gsd_run` launcher shim now probes all non-Claude runtime homes before failing.** The shim's last-resort detection previously stopped at `$HOME/.claude`, causing a false-positive fatal error on every non-Claude runtime (Hermes, Cursor, Codex, Copilot, Windsurf, Augment, Trae, Qwen, CodeBuddy, Cline, Grok, Antigravity, OpenCode, Kilo) when `RUNTIME_DIR` was unset and `gsd-tools` was not on `PATH`. The snippet now probes each runtime's config directory (respecting `HERMES_HOME`, `CURSOR_CONFIG_DIR`, `CODEX_HOME`, etc. with sensible `$HOME`-relative defaults) before emitting the install error.