emrg: upgrade-complete notification — GUI banner + one-click restart to apply

[argszero]

Summary

Host decision rant 2026-08-20T18:30:57: after auto-upgrade (#882) the user must be notified and able to apply the new version with one click (restart the daemon process — GUI restart does NOT restart the daemon; the daemon process must be restarted to load new code).

Changes (10 files, +195/−3)

1. daemon.py — pong response now carries current_version (reads ~/.emrg/install/version.txt; raw data only, zero judgment — GUI does the comparison). New _current_installed_version() helper.
2. main.js / preload.js — current_version passed through init + status events; new emrg:restartDaemon IPC sends shutdown (source=gui-restart). Restart path = GUI sends shutdown → connManager restart-recovery (all-drop within window) → ensureDaemon respawns the new code — GUI is already the daemon lifecycle owner, no subprocess CLI.
3. renderer app.js — tracks lastKnownVersion; maybeShowUpgradeBanner() compares each status pong and shows the banner on version change; restart button calls window.emrg.restartDaemon(); dismiss button hides.
4. index.html / layout.css — #upgrade-banner with message + restart button (reuses banner styles).
5. i18n.js — zh/en keys for banner message, restart button, failure toast.
6. Tests — daemon: pong includes current_version (+ missing-file → ""); GUI: banner shows on version change / stays hidden when unchanged / restart wiring asserts (renderer 125 pass).

Verification

• pytest full suite: 982 passed + 1 skipped (Agent.md count synced), import + CLI OK, daemon alive
• GUI: 254 tests = 247 pass + 7 integration fails (local-only by design, emrg: daemon single-instance via fixed-port bind exclusivity (rant 2026-08-19T08:05:21) #861)

Design notes

• No auto-restart: only the user clicking the button restarts (per host design — notify + user action, upgraded from verbal prompt to one-click button).
• The restart button is a product feature (user-initiated), NOT a test — it does not violate the ⛔ no-stop/restart-test red line (that covers test cases; a product restart button is normal functionality).

[argszero]

✅ LGTM — cycle 1 (10 files +195/−3: daemon pong carries current_version raw data; GUI compares lastKnownVersion → upgrade banner + one-click restart via shutdown + connManager respawn; tests: daemon current_version + GUI banner pos/neg + restart wiring; pytest 982 + GUI 247 green, test + test-windows CI PASS)

[argszero]

✅ LGTM — cycle 2 (independent re-review: daemon pong current_version + GUI upgrade banner + one-click restart; pytest 982 + GUI 247 green; test + test-windows CI PASS)

[argszero]

✅ LGTM — cycle 3 (independent re-review of the full diff: daemon pong current_version is raw data only; GUI maybeShowUpgradeBanner compares against lastKnownVersion with no-repeat guard; one-click restart via shutdown + connManager respawn is clean; daemon test covers present/missing file + pong payload; banner smoke tests cover pos/neg. pytest 982 + GUI 247 green, test + test-windows CI PASS)