fix(release): robust publisher fields, WAL-safe copy, installer tag order, pinned actions

From the full-repo Codex audit:
- The publisher read discovery fields one per line, so a report title
  with newlines shifted every later field and published a manifest
  without source.publish_date, which every client rejects (blocking all
  syncs). Read them NUL-separated, and refuse to write a manifest missing
  a field clients require.
- The snapshot builder copied the SQLite file with cp; committed data
  still in the -wal file of an open database would be missing. Checkpoint
  first (a no-op for the publisher's closed database, so the bytes and
  hash are unchanged) and refuse to copy when that cannot complete.
- install.sh took the tag from a greedy match, which on a compact
  single-line releases response picks the last tag, not the newest (it
  installed v0.2.3 over v0.2.4 in the new test). Split fields first.
- scripts/audit-msn-fundamentals.sh read the symbol map from a path that
  no longer exists and silently checked no stocks.
- release.yml granted contents: write to every job; only publish gets it
  now. Actions in the release and snapshot workflows are pinned to commit
  SHAs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3syn2fN2LNo5pvTSqc6eh

.github/workflows/publish-ownership-snapshot.yml

@@ -26,10 +26,10 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
 
       - name: Install Nix
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@08dcb3a5e62fa31e2da3d490afc4176ef55ecd72 # v30
 
       - name: Build ownership publisher
         run: nix build .#ownership-publisher
@@ -54,7 +54,7 @@ jobs:
 
       - name: Upload workflow artifact copy
         # A legitimate up-to-date run produces no new local artifacts.
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
           name: ownership-snapshot-${{ github.run_id }}
           path: dist/ownership-snapshot/*