docs: apply cross-model doc-review fixes for v1.73.0.0

- README.md: host table gains the OpenClaw explainer arm row (setup has the
  arm; the table claimed to match setup)
- docs/skills.md: /review completeness-gaps section documents the
  gstack-shortcut(dec-<id>) acknowledged-debt suppression and orphan-marker
  flagging; /autoplan deep-dive states the recommended-option default with
  the 6 principles as tie-breakers
- CONTRIBUTING.md: host count 8 -> 10 (Hermes, GBrain), supported-hosts list
  completed
- docs/TESTING_INTERNALS.md: sandbox recipe says to source ~/.bashrc after
  the doctor seeds it; GSTACK_FREE_JOBS wording fixed from "caps" to
  "overrides in either direction" (matches the un-clamped runner)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CONTRIBUTING.md

@@ -359,11 +359,11 @@ worth the review overhead.
 
 ## Multi-host development
 
-gstack generates SKILL.md files for 8 hosts from one set of `.tmpl` templates.
+gstack generates SKILL.md files for 10 hosts from one set of `.tmpl` templates.
 Each host is a typed config in `hosts/*.ts`. The generator reads these configs
 to produce host-appropriate output (different frontmatter, paths, tool names).
 
-**Supported hosts:** Claude (primary), Codex, Factory, Kiro, OpenCode, Slate, Cursor, OpenClaw.
+**Supported hosts:** Claude (primary), Codex, Factory, Kiro, OpenCode, Slate, Cursor, OpenClaw, Hermes, GBrain.
 
 ### Generating for all hosts
 
@@ -372,7 +372,7 @@ to produce host-appropriate output (different frontmatter, paths, tool names).
 bun run gen:skill-docs                    # Claude (default)
 bun run gen:skill-docs --host codex       # Codex
 bun run gen:skill-docs --host opencode    # OpenCode
-bun run gen:skill-docs --host all         # All 8 hosts
+bun run gen:skill-docs --host all         # All 10 hosts
 
 # Or use build, which does all hosts + compiles binaries
 bun run build