Closes #2493.

Summary

Adds three missing field initializers on RemoteClawApp (ui/src/ui/app.ts) that were dropped during partial-sync of upstream v2026.3.7 (9ef18943dc). The companion app-lifecycle.ts / app-gateway.ts / app-tool-stream.ts changes arrived (adding connectGeneration, serverVersion, chatStreamSegments to their host-shape types) but the class-level initializers silently conflicted with the OpenClawApp → RemoteClawApp rebrand and were dropped during merge resolution. The as unknown as Parameters<typeof X>[0] cast pattern in app.ts (21 occurrences) erased the structural type-check that would otherwise have flagged the missing fields.

Symptoms (from #2493)

• Fatal: connectGeneration undefined → ++undefined → NaN → NaN !== NaN is always true at app-lifecycle.ts:55 → connectGateway never called → Health Offline / Version n/a / "Disconnected from gateway." banner on first load.
• Latent crash: chatStreamSegments undefined → TypeError: not iterable when a tool call interrupts streaming text (app-tool-stream.ts:441 spreads it).
• Cosmetic: serverVersion undefined → incorrect client version in gateway handshake (optional-chained, no crash).

Fix

Three field initializers in RemoteClawApp, matching upstream type signatures and existing declaration styles:

• @state() serverVersion: string | null = null — reactive, feeds Version pill (grouped with other nullable gateway state near hello/lastError).
• @state() chatStreamSegments: Array<{ text: string; ts: number }> = [] — reactive, feeds chat streaming view (grouped with chatStream/chatStreamStartedAt).
• private connectGeneration = 0 — non-reactive lifecycle counter (grouped with chatHasAutoScrolled in the private bookkeeping section).

No test changes. Synthetic-host fixtures in app-lifecycle.node.test.ts / app-lifecycle-connect.node.test.ts already hand-set these fields — the problem was only in the production class.

Test plan

• pnpm tsgo clean (0 errors)
• pnpm lint clean (0 warnings, 0 errors)
• pnpm format:check clean
• pnpm exec vitest run --config vitest.unit.config.ts ui/src/ui/app-tool-stream.node.test.ts — 4/4 pass
• Full pnpm test — via CI
• Manual: chat dashboard connects on first load (Health=Online, Version populated) — deferred to post-merge smoke

Follow-ups (already filed per issue comment)

• refactor(ui): remove as unknown as Parameters<typeof X>[0] casts — restore structural type-checking #2494 — audit and remove as unknown as Parameters<typeof X>[0] casts so TypeScript catches future regressions of this class
• test(ui): add smoke test instantiating RemoteClawApp and asserting required host-interface fields #2495 — smoke test instantiating RemoteClawApp asserting required host-interface fields
• audit(ui): missing field initializers across PollingHost/ChatHost/SettingsHost/ScrollHost/CompactionHost on RemoteClawApp #2496 — audit other host-shape interfaces (Polling/Chat/Settings/Scroll/Compaction) for missing initializers