Fix 10 audit bugs: path prefix matching, verdict parsing, CORS, stale-task detection, phase mapping

Batch 1 (High severity):
- Bug 1: --audit cat3 now checks .automaton/tasks/ paths
- Bug 4: Verdict PASS/FAIL uses structured ## Status: line parsing
- Bug 5: register-guards.sh checks .json/.jsonc, writes plugin key, strips comments
- Bug 7: --can-edit/--scope-check path prefix uses os.sep boundary

Batch 2 (Medium/Low severity):
- Bug 2: migrate-project.sh find command parentheses for -prune binding
- Bug 3: vram_detect model prefix matching with known-suffix whitelist
- Bug 6: dashboard reads .state file before artifact heuristic fallback
- Bug 8: removed wildcard CORS, added security headers (nosniff, DENY)
- Bug 9: stale-task detection uses .state.lastedit instead of .state mtime
- Bug 10: TEST_PLAN.md maps to test_design (was implement)

249 tests pass (up from 235). All 10 tasks driven through full workflow to completion.

tasks/fix-register-guards/VERDICT.md

@@ -0,0 +1,29 @@
+# Verdict: fix-register-guards
+
+## Status: PASS
+**Completion Date**: 2026-06-22
+
+## Summary
+All three compounding bugs fixed. Documentation updated to reflect correct `plugin` key and both `.json`/`.jsonc` config files. One minor JSONC edge case noted but acceptable.
+
+## Findings
+- Config detection now checks both `opencode.json` and `opencode.jsonc`.
+- Writes to `plugin` (singular) key, preserving existing entries.
+- JSONC comment stripping handles line comments.
+- Manual install hint updated to use correct key and hardcoded path.
+- Bug Finder found no bugs. Adversarial Bug Finder noted the `//`-in-strings edge case but confirmed it's not blocking.
+- Doc Review: Updated `contracts/harness-integration.md`, `plugins/README.md`, and the script header comment.
+- No contradictions between reports.
+- All 242 tests pass; `bash -n` syntax check passes.
+
+## Tasks for Review / Tie-Breaks
+None.
+
+## Remaining Issues
+- JSONC comment stripping does not handle `//` inside string values (noted, acceptable for opencode config files).
+
+## Score
++10 (PASS)
+
+## Reviewer Comments
+