feat(#2792): namespace meta-skills + keyword-tag descriptions + context utilization guard (#2825)

* feat(#2792): namespace meta-skills retargeted at the post-#2790 surface

This branch is now based on #2790's HEAD (the consolidation PR) instead
of main, and every routing table targets the consolidated surface so a
user routed by a namespace meta-skill never lands at a deleted /
folded sub-skill.

Cross-PR inconsistencies the original PR #2825 carried (vs #2790):

  - ns-ideate routed to gsd-note / gsd-add-todo / gsd-add-backlog /
    gsd-plant-seed → all folded into gsd-capture by #2790. Now routes
    to gsd-capture (the parent picks the mode from the user's intent).
  - ns-context routed to gsd-scan and gsd-intel → folded into
    gsd-map-codebase --fast / --query by #2790. Now routes to those
    flag forms.
  - ns-manage routed all workspace intent to gsd-list-workspaces (a
    list-only entry) → CR also flagged the over-narrow target. #2790
    folds into gsd-workspace; routing now points there.
  - ns-workflow routed to gsd-research-phase → deleted outright by
    #2790. Removed.
  - ns-project routed to gsd-plan-milestone-gaps → deleted outright by
    #2790. Removed.
  - None of the namespaces previously surfaced #2790's new consolidated
    skills (gsd-capture, gsd-phase, gsd-config, gsd-workspace,
    gsd-progress). All five are now reachable through the routers.
  - extract_learnings → extract-learnings (canonicalized by #2858).

Defect fixes within the namespace skills:

  - Hyphen-form `name:` (gsd-workflow, …) per the canonical naming
    contract — the colon-form addressed CR's drift complaint.
  - `Skill` added to allowed-tools on every router. The body instructs
    "Invoke the matched skill directly using the Skill tool" — without
    Skill in the permission list the meta-skill cannot route at all.

New regression guard in tests/enh-2792-namespace-skills.test.cjs: every
gsd-* token in any namespace router's table column resolves to a
surviving commands/gsd/*.md file (or to a known consolidated parent for
flag-form targets like gsd-map-codebase --fast). This single test would
have caught every dead-end route the original PR shipped with.

Skill-count cap in tests/enh-2790-skill-consolidation.test.cjs now
filters out ns-*.md from its <= 63 cap. Namespace routers are
descriptor-only entries, not part of the consolidation surface that cap
is policing — they have their own contract in
tests/enh-2792-namespace-skills.test.cjs.

INVENTORY.md gains a "Namespace Meta-Skills" section with the 6 router
rows; INVENTORY-MANIFEST.json gains 6 entries; the headline count moves
59 → 65 to match.

Out of scope for this rebase: the gsd-health --context flag (PR #2825
advertised the contract but didn't implement it). That's a separate
feature concern and is left untouched here.

5908/5908 on `npm test`.

* feat(#2792): implement gsd-health --context utilization guard

The original PR #2825 advertised a `--context` flag on gsd-health with a
60%/70% utilization threshold table but never implemented the workflow
logic — CR caught it as a contract leak, the rebase deferred it. This
commit closes the gap with TDD red/green/refactor.

Math layer (pure):
  - get-shit-done/bin/lib/context-utilization.cjs
    classifyContextUtilization(tokensUsed, contextWindow) →
      { percent, state }
    State boundaries use the exact ratio:
      < 60% healthy / 60–70% warning / ≥ 70% critical (fracture point)
    Display percent rounded for humans. Throws TypeError on non-integer
    or out-of-range inputs.
  - STATES = Object.freeze({ HEALTHY, WARNING, CRITICAL }) exported
    so callers reference the names by symbol, not by literal string.

SDK CLI integration:
  - get-shit-done/bin/gsd-tools.cjs
    `validate context --tokens-used N --context-window M [--json]`
    routes to the classifier, owns the recommendation copy (the
    classifier intentionally does not — keeps the renderer free to
    evolve without touching the math layer or its tests), and uses
    core.output's rawValue path for the sync-flush guarantee.
  - sdk/src/query/validate.ts + sdk/src/query/index.ts
    TypeScript validateContext handler registered at 'validate.context'
    and 'validate context'. Mirrors the CJS classifier inline (15 lines
    of arithmetic; not worth a shared cross-language module).

User-facing wiring:
  - commands/gsd/health.md frontmatter advertises --context, body
    documents the three-state threshold table.
  - get-shit-done/workflows/health.md adds a `context_check` step
    that's reached only when --context is set. Step calls
    `gsd-sdk query validate.context` with self-reported tokensUsed and
    contextWindow, prints the SDK output verbatim, and ends. Includes
    a TEXT_MODE plain-text fallback for non-Claude runtimes per #2012.

Tests:
  - tests/context-utilization.test.cjs (17 tests) — pure-function
    contract: state thresholds at every boundary, percent rounding,
    input validation, return-shape (no recommendation field — that's
    the renderer's job).
  - tests/validate-context.test.cjs (9 tests) — SDK CLI plumbing:
    arg parsing errors, JSON vs human rendering, recommendation copy
    pinned per state.
  - tests/enh-2792-namespace-skills.test.cjs (4 new tests) — markdown
    contract: --context advertised in argument-hint, threshold table
    in command body, context_check step exists in workflow, step
    invokes gsd-sdk query validate.context with both flags.

Inventory bookkeeping:
  - docs/INVENTORY.md "CLI Modules" 31 → 32; new row for
    context-utilization.cjs.
  - docs/INVENTORY-MANIFEST.json mirror.

5939/5939 on `npm test`.

get-shit-done/bin/gsd-tools.cjs

@@ -792,8 +792,48 @@ async function runCommand(command, args, cwd, raw, defaultValue) {
         verify.cmdValidateHealth(cwd, { repair: repairFlag, backfill: backfillFlag }, raw);
       } else if (subcommand === 'agents') {
         verify.cmdValidateAgents(cwd, raw);
+      } else if (subcommand === 'context') {
+        // The model self-reports tokensUsed and contextWindow — the SDK has
+        // no privileged access to either. Recommendation copy lives here
+        // (the renderer), not in the classifier, so it can change without
+        // re-validating the math layer.
+        const opts = parseNamedArgs(args, ['tokens-used', 'context-window']);
+        if (opts['tokens-used'] === null) {
+          error('--tokens-used <integer> is required for `validate context`');
+          break;
+        }
+        if (opts['context-window'] === null) {
+          error('--context-window <integer> is required for `validate context`');
+          break;
+        }
+        const { classifyContextUtilization, STATES } = require('./lib/context-utilization.cjs');
+        const RECOMMENDATIONS = {
+          [STATES.HEALTHY]: null,
+          [STATES.WARNING]: 'Context is approaching the fracture zone — consider /gsd-thread to continue in a fresh window.',
+          [STATES.CRITICAL]: 'Reasoning quality may degrade past 70% utilization (fracture point). Run /gsd-thread now to preserve output quality.',
+        };
+        let classified;
+        try {
+          classified = classifyContextUtilization(Number(opts['tokens-used']), Number(opts['context-window']));
+        } catch (e) {
+          // Translate the classifier's TypeError into a CLI-shaped error
+          // message that names the offending flag.
+          const flag = /tokensUsed/.test(e.message) ? '--tokens-used' : '--context-window';
+          error(`${flag} must be a non-negative integer (window > 0), got the values supplied`);
+          break;
+        }
+        const result = { ...classified, recommendation: RECOMMENDATIONS[classified.state] };
+        if (args.includes('--json')) {
+          core.output(result, raw);
+        } else {
+          const lines = [`Context utilization: ${result.percent}% (${result.state})`];
+          if (result.recommendation) lines.push(result.recommendation);
+          // Use core.output's rawValue path for the sync-flush guarantee
+          // — process.stdout.write can be truncated on process exit.
+          core.output(result, true, lines.join('\n'));
+        }
       } else {
-        error('Unknown validate subcommand. Available: consistency, health, agents');
+        error('Unknown validate subcommand. Available: consistency, health, agents, context');
       }
       break;
     }