emrg: upgrade prompt: enforce GUI sync with self-sufficient toolchain

[argszero]

What

Makes GUI sync a mandatory step of the auto-upgrade flow. Previously the upgrade prompt treated the GUI (EMRG.app) as "your call — skip if no node/npm", which left GUI packages stuck at 0.2.72 while the daemon moved on.

Root cause of the old skip reasoning: a false premise — node/npm exist on the host (asdf), they are just not on the daemon's PATH.

Changes (emrg/server/prompts/upgrade_prompt.j2)

Replaces the optional "GUI as needed" paragraph with a fixed 5-step GUI must-sync flow:

1. Version compare — extract package.json from the installed GUI asars ({{ install_dir }}/emrg-gui/... and ~/Applications/EMRG.app) via npx @electron/asar extract-file and compare with the target tag's emrg/gui/package.json version. Identical → skip build but still do the copy/sync check.
2. Toolchain self-sufficiency — inside {{ upgrade_work }}, never assume node/npm are callable; try in order: asdf shims (~/.asdf/shims), nvm, Homebrew, last-resort node LTS binary tarball download. Verify node --version && npm --version before building.
3. Build the GUI — mirror CI's build-release.yml order: build-runtime.sh if dist/runtime is missing, then npm install && npm run dist → dist/mac-arm64/EMRG.app. Host-arch-only build is fine (release installer rebuilds all arches); electron-builder ad-hoc signing is part of the build output, not manual signing/notarization.
4. Replace — back up both {{ install_dir }}/emrg-gui/EMRG.app and ~/Applications/EMRG.app into {{ backup_dir }}/<current_version>/ (emrg-gui tree was previously excluded from backups — now included), then copy the fresh build to both locations (postinstall semantics: emrg-gui/EMRG.app = install source, ~/Applications/EMRG.app = run copy).
5. Verify — re-extract the replaced asar's package.json and confirm version == target tag (strip leading v).

Verification

• Full pytest: 1039 passed, 1 skipped (prompt template change; no daemon logic touched)

Rant: 2026-08-24T17:52:03 (upgrade_prompt.j2 强制 GUI 同步升级 — 工具链自给自足)

[argszero]

✅ LGTM — cycle 180730

Re-verified: head 4e135a5 unchanged, MERGEABLE/CLEAN, CI green (test + test-windows). Reviewed upgrade_prompt.j2: GUI 'as needed' → mandatory 5-step sync flow (asar version compare → self-sufficient toolchain asdf/nvm/brew/fallback download → CI-mirroring build → backup+replace both install paths → asar version verify). No jinja/directive changes, prompt-only — local pytest 1039 pass / 1 skip.

[argszero]

✅ LGTM — cycle 181352

Re-verified: head 4e135a5 unchanged, MERGEABLE/CLEAN, CI green (test + test-windows). Prompt-only change (upgrade_prompt.j2): GUI must-sync 5-step flow with self-sufficient toolchain fallbacks (asdf/nvm/brew/download), backup both app paths, asar version verification. No jinja directives touched — LGTM.

[argszero]

✅ LGTM — cycle 182004 (3/3)

Re-verified: head 4e135a5 unchanged, MERGEABLE/CLEAN, CI green (test + test-windows). Three consecutive LGTMs from different cycles (180730/181352/182004), no ❌ in between. Merge approved.