refactor(tests): retire output-grep & source-grep via typed surfaces (finish #2974) (#462)

* refactor(#455): implement typed surfaces to retire grep tests

Production surfaces added:
- hooks/managed-hooks-registry.cjs: new CJS module exporting MANAGED_HOOKS
  as a typed array; gsd-check-update-worker.js now requires it instead of
  declaring an inline array
- bin/install.js: elevate inline gsdHooks to module-level GSD_UNINSTALL_HOOKS,
  export it alongside runtimeMap/allRuntimes (already exported)
- scripts/build-hooks.js: export HOOKS_TO_COPY; guard build() behind
  require.main===module so tests can require the file without triggering a build
- get-shit-done/bin/lib/init.cjs: add --json mode to agent-skills command,
  emitting typed IR { agent_type, block, skills_count } for test assertions
- get-shit-done/bin/gsd-tools.cjs: wire --json flag for agent-skills dispatch

Category-B source-grep migrations:
- tests/managed-hooks.test.cjs: require MANAGED_HOOKS from registry, drop fs.readFileSync+regex
- tests/orphaned-hooks.test.cjs: require MANAGED_HOOKS+HOOKS_TO_COPY as typed exports
- tests/hooks-opt-in.test.cjs: replace gsdHooks regex-parse with GSD_UNINSTALL_HOOKS import
- tests/install-minimal-hooks.test.cjs: replace gsdHooks regex-parse with GSD_UNINSTALL_HOOKS
- tests/copilot-install.test.cjs: replace src.includes() checks with typed
  assertions on runtimeMap, allRuntimes, parseRuntimeInput, buildRuntimePromptText
- tests/agent-skills.test.cjs: migrate to --json typed IR assertions

pending-migration-to-typed-ir token cleared (87 of 87 files):
- 78 files already had source-text-is-the-product; removed duplicate token
- 5 files already used typed assertions; reclassified or annotated
- 4 files required individual reclassification to source-text-is-the-product
  or architectural-invariant

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(#455): update workflow-guard test to typed GSD_UNINSTALL_HOOKS import; isolate HOME in runtime-launcher (D) test

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(#455): guard install.js main() behind require.main===module so the typed export is require-safe

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(#455): document --json typed surfaces for agent-skills, progress, validate context

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(#455): add changeset fragment for new --json surfaces

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(#455): complete grep migration for files flagged by lint-tests

The branch commit 4e630d99 stripped `allow-test-rule: pending-migration-to-typed-ir`
from ~80 test files without replacing their assertions or adding the correct
exemption annotation. The files were NOT source-grep tests — they read .md
workflow/agent/command/reference files (source-text-is-the-product) or hook
source files for structural invariants (structural-regression-guard). No
assertion logic was changed; only the correct allow-test-rule annotation was
added to each file per CONTRIBUTING.md exception matrix.

73 files: `source-text-is-the-product` — workflow/agent/command/reference .md
7 files:  `structural-regression-guard` — hook .js / bin/install.js structural checks

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: CI Rebase Check <ci@gsd-redux>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/bug-patterns-reference.test.cjs

@@ -1,7 +1,7 @@
-// allow-test-rule: pending-migration-to-typed-ir [#2974]
-// Tracked in #2974 for migration to typed-IR assertions per CONTRIBUTING.md
-// "Prohibited: Raw Text Matching on Test Outputs". Per-file review may
-// reclassify some entries as source-text-is-the-product during migration.
+// allow-test-rule: source-text-is-the-product
+// Workflow .md / agent .md / command .md / reference .md files — their text
+// IS what the runtime loads. Testing text content tests the deployed contract.
+// Per CONTRIBUTING.md exception matrix.
 
 /**
  * Common Bug Patterns Reference Tests