fix(watcher): park through the brain root, keep a note edited mid-resolve, honour only real fences (#205)

From the second independent review of #207:
- parkForReview now skips the delete when the note changed since it was read
  (an LLM call sits in that window; Syncthing can deliver a newer version)
- parked copies are created via brainfs (real dirs only, O_EXCL, no symlink
  following), so a planted raw/needs-review symlink cannot redirect or hide a
  note; this also removes the need for the guard allowlist entry added in
  1e14c56, which is reverted
- a '----' line no longer closes the proposal block
Each has a test that failed first and a mutant that fails it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ingestion/internal/extract/callsites_test.go

@@ -89,9 +89,6 @@ func TestNoPackageReferencesExtractTextOutsideExtract(t *testing.T) {
 // on a path that is not a raw/ read.
 var osOpenAllowed = map[string]bool{
 	"internal/watcher/watcher.go:appendWatcherLog": true, // ingest log append, not a raw/ read
-	// Claims a free name in raw/needs-review/ with O_EXCL so a parked note is
-	// never overwritten (#205). It creates a file; it reads nothing from raw/.
-	"internal/watcher/watcher.go:reserveParkedName": true,
 	// Text reads by path; outside this package only TextIn's temp copy reaches
 	// it (TestNoPackageReferencesExtractTextOutsideExtract enforces that).
 	"internal/extract/extract.go:Text": true,