chore(#3546): migrate hook advisory assertions onto typed output surfaces (#4167)

* chore(#3546): migrate hook advisory assertions onto typed output surfaces

Add additive typed fields to 5 hook scripts' PreToolUse/PostToolUse
advisory output alongside the existing additionalContext prose:

- gsd-read-guard.js: code ('READ_BEFORE_EDIT'), fileName
- gsd-context-monitor.js: severity ('warning'|'critical')
- gsd-prompt-guard.js: findings ([{ruleId, match}], module-local RULE_IDS
  + renderFinding mapper mirroring gsd-read-injection-scanner.js's #3523
  pattern)
- gsd-read-injection-scanner.js: severity ('LOW'|'HIGH'), source (its
  findings array already existed from #3523)
- gsd-workflow-guard.js: code ('WORKFLOW_ADVISORY') on the advisory leg,
  distinct from the existing force-add block leg's code

additionalContext stays byte-identical in every hook (verified per-hook
against the pristine HEAD version across a spread of payload shapes).

Migrates all 20 assertion sites named in the issue off
additionalContext.includes(...)/assert.match(...) substring-matching
onto the new typed fields, per CONTRIBUTING.md's prohibition on raw
text matching on test outputs.

Closes #3546

* test: fix undersized commit-class timeout in gsd-statusline.test.cjs's commitN helper

Surfaced by gsd-test on the #3546 checkpoint: `commitN()`'s loop called
gitOrThrow(['add','-A']/['commit',...]) without a timeoutMs override, so
each call used DEFAULT_GIT_TIMEOUT_MS (15s) -- a bound git-fixture.cjs's
own doc comment says is sized for plumbing reads (rev-parse/branch/log),
not write-heavy add/commit spawns. That file already documents the exact
same defect class from a prior incident (PR #3323) and exports
GIT_FIXTURE_TIMEOUT_MS (60s) for fixture-construction call sites -
commitN just wasn't using it. Observed failure: `git commit -m filler 9`
timed out under normal bench load, unrelated to any of this PR's own
diff (hooks/*.js + 5 other test files).

Not a flake: root-caused to the timeout bound being sized for the wrong
call class, per this repo's no-flakes rule.

* chore(#3546): backfill changeset PR number (#4167)

---------

Co-authored-by: sim <sim@local>

tests/read-guard.test.cjs

@@ -84,9 +84,10 @@ describe('gsd-read-guard hook', () => {
     const output = JSON.parse(result.stdout);
     assert.ok(output.hookSpecificOutput, 'should have hookSpecificOutput');
     assert.ok(output.hookSpecificOutput.additionalContext, 'should have additionalContext');
-    assert.ok(
-      output.hookSpecificOutput.additionalContext.includes('Read'),
-      'guidance should mention Read tool'
+    assert.equal(
+      output.hookSpecificOutput.code,
+      'READ_BEFORE_EDIT',
+      'guidance should carry the READ_BEFORE_EDIT reason code'
     );
   });
 
@@ -103,7 +104,7 @@ describe('gsd-read-guard hook', () => {
     assert.ok(result.stdout.length > 0, 'should produce output');
 
     const output = JSON.parse(result.stdout);
-    assert.ok(output.hookSpecificOutput.additionalContext.includes('Read'));
+    assert.equal(output.hookSpecificOutput.code, 'READ_BEFORE_EDIT');
   });
 
   // ─── No-op cases: should NOT inject guidance ────────────────────────────
@@ -179,9 +180,10 @@ describe('gsd-read-guard hook', () => {
     });
 
     const output = JSON.parse(result.stdout);
-    assert.ok(
-      output.hookSpecificOutput.additionalContext.includes('myfile.ts'),
-      'guidance should include the filename being edited'
+    assert.equal(
+      output.hookSpecificOutput.fileName,
+      'myfile.ts',
+      'guidance should name the file being edited'
     );
   });
 
@@ -348,7 +350,7 @@ describe('bug #2344: read guard skips on CLAUDECODE env var', () => {
     assert.equal(result.exitCode, 0);
     assert.ok(result.stdout.length > 0, 'advisory should fire on non-Claude-Code runtimes');
     const output = JSON.parse(result.stdout);
-    assert.ok(output.hookSpecificOutput?.additionalContext?.includes('Read'));
+    assert.equal(output.hookSpecificOutput?.code, 'READ_BEFORE_EDIT');
   });
 });
   });
@@ -487,7 +489,7 @@ describe('bug #2520: read guard detects Claude Code without relying on CLAUDECOD
     assert.equal(result.exitCode, 0);
     assert.ok(result.stdout.length > 0, 'advisory should fire on non-Claude-Code hosts');
     const output = JSON.parse(result.stdout);
-    assert.ok(output.hookSpecificOutput?.additionalContext?.includes('Read'));
+    assert.equal(output.hookSpecificOutput?.code, 'READ_BEFORE_EDIT');
   });
 });
   });
@@ -529,7 +531,7 @@ describe('#2304: Kimi tool vocabulary is normalized by the read guard', () => {
     assert.equal(result.exitCode, 0);
     assert.ok(result.stdout.length > 0, 'Kimi WriteFile should produce the advisory');
     const output = JSON.parse(result.stdout);
-    assert.ok(output.hookSpecificOutput?.additionalContext?.includes('Read'));
+    assert.equal(output.hookSpecificOutput?.code, 'READ_BEFORE_EDIT');
   });
 
   test('StrReplaceFile on an existing file injects guidance like Edit', () => {
@@ -544,7 +546,7 @@ describe('#2304: Kimi tool vocabulary is normalized by the read guard', () => {
     assert.equal(result.exitCode, 0);
     assert.ok(result.stdout.length > 0, 'Kimi StrReplaceFile should produce the advisory');
     const output = JSON.parse(result.stdout);
-    assert.ok(output.hookSpecificOutput?.additionalContext?.includes('Read'));
+    assert.equal(output.hookSpecificOutput?.code, 'READ_BEFORE_EDIT');
   });
 
   test('module-qualified kimi_cli.tools.file:WriteFile is recognized', () => {