workstation: per-user playwright browser MCP for all users, reproducible from git

Viktor asked that the playwright browser MCP be available for every devvm user
in every directory, with each user running their own server and multiple
concurrent sessions per user.

Before this, playwright was hand-set-up per user (~/.config/systemd/user/
playwright-mcp.service on 8931/8932/8933) and only wizard was actually wired —
emo's and anca's servers ran but their ~/.claude.json had no playwright entry,
so their Claude never connected. None of it was reproducible from git (units,
refresh script, and the Vault snapshot token lived only in user homes), so a
devvm rebuild would silently lose it.

This makes it reproducible and fixes the unwired users:

- roster_engine.py: sticky per-user PLAYWRIGHT_PORT (PLAYWRIGHT_BASE_PORT=8931,
  allocated for every roster user incl. the admin), emitted in the derive JSON.
- scripts/workstation/playwright/: system-level TEMPLATE units
  (playwright-mcp@.service + playwright-snapshot-refresh@.{service,timer},
  User=%i — system manager, so no systemd --user / linger) + the refresh script.
  @playwright/mcp pinned to 0.0.76 (avoids the @latest silent-fleet-roll
  footgun, same rationale as T3_PIN).
- setup-devvm.sh: install the templates + script (9e); stage the chrome-service
  snapshot bearer token from Vault to a root file (8c) — the hourly root
  reconcile has no Vault token, mirrors the Claude OAuth staging in 8a.
- t3-provision-users.sh: install_playwright() (ALL tiers incl. admin) writes
  PLAYWRIGHT_PORT, seeds the token if-absent, wires the user-scope ~/.claude.json
  by running `claude mcp add` AS the user (clobber-proof + if-absent, so it fixes
  existing/new/admin without rewriting a populated config), and enable --now's the
  instances (idempotent, never restarts a running server). Also hardened the
  section-1 *.env scan to skip the new playwright-*.env files (no T3_PORT -> grep
  no-match would abort under set -e -o pipefail).
- Docs: chrome-service-snapshot runbook (new Provisioning section + system-unit
  commands), multi-tenancy.md, and the 2026-06-07 plan Task 2.3.

Supersedes the hand-made per-user --user units (one-time idle-gated migration to
follow on the live host).

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

scripts/workstation/playwright/playwright-snapshot-refresh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+# Refresh the local cookie+localStorage snapshot served by chrome-service.
+#
+# Run per-user by the hourly playwright-snapshot-refresh@<user>.timer systemd
+# unit (as that user, so $HOME resolves to the user's home). Per-session Claude
+# Code MCP contexts (`@playwright/mcp --isolated --storage-state=…`) read this
+# file on each connection — fresh state is visible to NEW sessions, existing
+# ones keep what they were seeded with.
+#
+# Token: cached at ~/.config/playwright/token. Seeded per-user (if-absent) by
+#   t3-provision-users.sh from the root-staged /etc/t3-serve/chrome-service-token
+#   (which setup-devvm.sh writes from Vault `secret/chrome-service`
+#   api_bearer_token). Rotate by re-staging + re-copying; the snapshot endpoint
+#   reloads the token via Reloader, local caches must be refreshed.
+set -euo pipefail
+
+URL="${PLAYWRIGHT_SNAPSHOT_URL:-https://chrome.viktorbarzin.me/api/snapshot}"
+TOKEN_FILE="${PLAYWRIGHT_SNAPSHOT_TOKEN:-$HOME/.config/playwright/token}"
+DEST="${PLAYWRIGHT_SNAPSHOT_PATH:-$HOME/.cache/playwright-shared-storage-state.json}"
+
+if [ ! -r "$TOKEN_FILE" ]; then
+  echo "ERROR: token file $TOKEN_FILE missing or unreadable" >&2
+  exit 1
+fi
+
+mkdir -p "$(dirname "$DEST")"
+TMP="$DEST.new.$$"
+trap 'rm -f "$TMP"' EXIT
+
+TOKEN="$(cat "$TOKEN_FILE")"
+
+HTTP_CODE=$(curl -sS \
+  -H "Authorization: Bearer $TOKEN" \
+  -o "$TMP" \
+  -w '%{http_code}' \
+  --max-time 30 \
+  "$URL")
+
+if [ "$HTTP_CODE" != "200" ]; then
+  echo "ERROR: HTTP $HTTP_CODE from $URL" >&2
+  cat "$TMP" >&2
+  exit 1
+fi
+
+# Sanity: response must be valid JSON with at least the cookies/origins keys.
+python3 - "$TMP" <<'PY' || { echo "ERROR: response is not a valid storageState JSON" >&2; exit 1; }
+import json, sys
+with open(sys.argv[1]) as f:
+    data = json.load(f)
+if "cookies" not in data or "origins" not in data:
+    raise SystemExit("missing required keys")
+PY
+
+mv -f "$TMP" "$DEST"
+trap - EXIT
+chmod 600 "$DEST"
+echo "snapshot refreshed: $DEST ($(stat -c %s "$DEST") bytes)"