fix(fleet): harden #791 upgrade rollback against find/reset failures

Second- and third-round independent-review reliability fixes on the keep-mode
upgrade rollback path, plus accurate abort messaging. All fixed red-first with
self-verifying controls in the rollback gate.

Round 2 (blockers A/B, should-fix C):
- install.sh: `trap 'restore_snapshot; exit 1' ERR INT TERM` so an INT/TERM
  mid-sync terminates instead of resuming past the interrupt and reporting
  success (a bash signal handler that only returns does not terminate).
- manifest.{ts,sh}: reject a degenerate [framework] section whose entries are
  all empty or bare-dot (`/`, `./`, `.`, `..`) — it passed the non-empty guard
  yet yielded zero usable globs, silently resolving everything to operator.
  Parity via a shared `[^/.]` usable-glob test; TS throws ManifestError.
- finalize.ts: classify the sync-abort message — a ManifestError is a pre-sync
  validation abort ("no files were changed"); any other error may be partial.

Round 3 (blockers D1, D2):
- install.sh: enumerate framework files with a checked temp file (_scan_or_die)
  instead of `< <(find …)` — process substitution discards find's exit status,
  so an EACCES/I/O failure mid-scan would truncate the file list yet leave the
  loop exiting 0, committing a partial upgrade as success (ERR trap never fires).
- install.sh: guard the `rm -rf; mkdir -p` target reset inside restore_snapshot
  — a bare reset failing under set -e exits silently after partial deletion,
  never printing the snapshot-recovery pointer. Now checked like the cp -a
  restore: on failure it preserves the snapshot and tells the operator where.

Tests: rollback gate 14→28 (Parts C/D/E with disabled-guard controls);
new finalize-sync-abort.spec.ts (3). No secret value is ever emitted; snapshots
stay 0700. Gates green: typecheck, lint, format:check, full mosaic vitest 1094,
HARD GATE 193, rollback 28, migration 21.

Refs #791

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.woodpecker/ci.yml

@@ -44,14 +44,19 @@ steps:
 
   # Blocking gate (#791): a framework upgrade must never write or delete an
   # operator-owned path. The HARD GATE proves an unanticipated operator sentinel
-  # survives a keep-mode reseed byte-identical (both rsync + cp paths); the
-  # migration matrix pins the v2→v3 contract-file semantics. Pure bash, no
-  # node_modules — runs early alongside sanitization.
+  # survives a keep-mode reseed byte-identical (with rsync present AND absent —
+  # keep mode is a single cp-based path that must not depend on rsync), and that a
+  # corrupt/empty/missing manifest aborts fail-closed leaving operator files
+  # untouched (B2/B3). The rollback gate proves a mid-sync failure is rolled back
+  # from the pre-update snapshot (B1). The migration matrix pins the v2→v3
+  # contract-file semantics. Pure bash, no node_modules — runs early alongside
+  # sanitization.
   upgrade-guard:
     image: *node_image
     commands:
       - apk add --no-cache bash rsync
       - bash packages/mosaic/framework/tools/quality/scripts/test-upgrade-manifest-guard.sh
+      - bash packages/mosaic/framework/tools/quality/scripts/test-upgrade-rollback.sh
       - bash packages/mosaic/framework/tools/quality/scripts/test-install-migration.sh
 
   typecheck: