feat(framework): P4 (2/2) — TS installer parity + fixtures + fail-closed init

Mirror install.sh's upgrade-safe migration in the npm/TS install path and lock it
with CI-gating fixtures:
- file-adapter.ts: FRAMEWORK_OWNED_FILES (overwrite, backup-once to
  .pre-constitution.bak) vs USER_SEEDED_FILES (seed-if-absent); CONSTITUTION.md
  added to preserve; reconcile mirrors reconcile_framework_files() in install.sh
- file-adapter.test.ts: 5 migration fixtures (overwrite framework-owned + backup,
  idempotent backup-once, preserve SOUL/credentials, preserve user-seeded TOOLS);
  updated the prior "preserve AGENTS" test that P4 intentionally inverts
- mosaic-init: fail-closed persona — --name is REQUIRED in --non-interactive mode
  (no silent agent named "Assistant"); verified exit 1 + clear error
- verify-sanitized.sh self-test: prove the identity scan actually covers
  *.yaml/*.service config formats (Claude review ticket)

Both installers now behave identically. install.sh fixture suite 14/14 green;
gate green; mosaic-init fail-closed verified.

Refs #542

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/mosaic/framework/tools/quality/scripts/verify-sanitized.sh

@@ -53,9 +53,15 @@ _selftest() {
   local tmp; tmp="$(mktemp -d)" || return 1
   printf 'contact jason.woltje at jarvis-brain (PDA-friendly)\n' > "$tmp/planted.md"
   printf 'X="${VAR:-$HOME/src/whatever/x.json}"\n' > "$tmp/planted.sh"
+  printf 'name: jason-woltje\n' > "$tmp/planted.yaml"
+  printf '[Service]\nUser=jarvis\n' > "$tmp/planted.service"
   local rc=0
   grep -qIEi "$DENYLIST" "$tmp/planted.md" || { echo "✗ SELF-TEST: identity denylist regex broken" >&2; rc=1; }
   grep -qIE  "$STRUCTURAL_SH" "$tmp/planted.sh" || { echo "✗ SELF-TEST: structural regex broken" >&2; rc=1; }
+  # Prove the identity scan covers the config formats it claims to (yaml/service/etc).
+  local n_ext
+  n_ext=$(find "$tmp" -type f \( -name '*.yaml' -o -name '*.service' \) -print0 | xargs -0 -r grep -lIEi "$DENYLIST" 2>/dev/null | wc -l)
+  [[ "$n_ext" -eq 2 ]] || { echo "✗ SELF-TEST: identity scan does not cover .yaml/.service extensions" >&2; rc=1; }
   rm -rf "$tmp"; return $rc
 }
 _selftest || exit 2