feat: add settings layers to /gsd-settings (Group A toggles) (closes #2527) (#2602)

* feat(#2527): add settings layers to /gsd:settings (Group A toggles)

Expand /gsd:settings from 14 to 22 settings, grouped into six visual
sections: Planning, Execution, Docs & Output, Features, Model & Pipeline,
Misc. Adds 8 new toggles:

  workflow.pattern_mapper, workflow.tdd_mode, workflow.code_review,
  workflow.code_review_depth (conditional on code_review=on),
  workflow.ui_review, commit_docs, intel.enabled, graphify.enabled

All 8 keys already existed in VALID_CONFIG_KEYS and docs/CONFIGURATION.md;
this wires them into the interactive flow, update_config write step,
~/.gsd/defaults.json persistence, and confirmation table.

Closes #2527

* test(#2527): tighten leaf-collision and rename mismatched negative test

Addresses CodeRabbit findings on PR #2602:

- comment 3127100796: leaf-only matching collapsed `intel.enabled` and
  `graphify.enabled` to a single `enabled` token, so one occurrence
  could satisfy both assertions. Replace with hasPathLike(), which
  requires each dotted segment to appear in order within a bounded
  window. Applied to both update_config and save_as_defaults blocks.

- comment 3127100798: the negative-test description claimed to verify
  invalid `code_review_depth` value rejection but actually exercised an
  unknown key path. Split into two suites with accurate names: one
  asserts settings.md constrains the depth options, the other asserts
  config-set rejects an unknown key path.

* docs(#2527): clarify resolved config path for /gsd-settings

Addresses CodeRabbit comment 3127100790 on PR #2602: the original line
implied a single `.planning/config.json` target, but settings updates
route to `.planning/workstreams/<active>/config.json` when a workstream
is active. Document both resolved paths so the merge target is
unambiguous.

docs/COMMANDS.md

@@ -1037,7 +1037,16 @@ Manage parallel workstreams for concurrent work on different milestone areas.
 
 ### `/gsd-settings`
 
-Interactive configuration of workflow toggles and model profile.
+Interactive configuration of workflow toggles and model profile. Questions are grouped into six visual sections:
+
+- **Planning** — Research, Plan Checker, Pattern Mapper, Nyquist, UI Phase, UI Gate, AI Phase
+- **Execution** — Verifier, TDD Mode, Code Review, Code Review Depth _(conditional — only when Code Review is on)_, UI Review
+- **Docs & Output** — Commit Docs, Skip Discuss, Worktrees
+- **Features** — Intel, Graphify
+- **Model & Pipeline** — Model Profile, Auto-Advance, Branching
+- **Misc** — Context Warnings, Research Qs
+
+All answers are merged via `gsd-sdk query config-set` into the resolved project config path (`.planning/config.json` for a standard install, or `.planning/workstreams/<active>/config.json` when a workstream is active), preserving unrelated keys. After confirmation, the user may save the full settings object to `~/.gsd/defaults.json` so future `/gsd-new-project` runs start from the same baseline.
 
 ```bash
 /gsd-settings                       # Interactive config