feat(sessions): support automatic conversation naming

[wen2zhou]

Problem

New conversations keep prompt-derived fallback labels instead of receiving concise titles consistently. Provider-native titles can also arrive late, race Session persistence, or be unavailable, while Claude title metadata reads can delay an otherwise completed turn.

Proposed change

• Request automatic naming only for the first visible user turn.
• Prefer framework-native titles from Claude Code and OpenCode.
• Preserve the restricted, tool-less LLM title generator as a fallback after a short framework grace period.
• Attribute naming usage to the first Conversation Turn and persist title updates atomically across main, preload, renderer, task, and web-service paths.
• Bound Claude SDK title reads to 250 ms so title metadata cannot hold prompt completion open.
• Serialize renderer title mutations through the existing ordered Session persistence seam.

Scope and non-goals

• This changes Session naming, naming-usage attribution, and persistence only.
• It does not change the visible workspace layout or introduce database schema changes.
• It does not remove the app-generated LLM fallback; providers without a timely native title still receive an automatic title.

Acceptance criteria and validation

All listed checks ran after the final material edit.

• Cross-process types and contracts → npm run typecheck → passed.
• Repository lint rules → npm run lint → passed with 0 errors; 11 pre-existing warnings outside this change.
• Portable ACP, persistence, task, renderer, preload, shared, and web behavior → npm test → 1,001 files and 14,640 tests passed; 15 files and 209 tests skipped.
• Claude ACP patch integrity → npm run check:claude-acp-patch → passed.
• Clean package patch applicability → reinstall @agentclientprotocol/claude-agent-acp@0.60.0, then npx patch-package → passed.
• Whitespace integrity → git diff --check → passed.
• Independent final-diff review → no P1/P2 correctness or maintainability findings.

UI E2E was excluded because the change does not modify visual structure or interaction controls. The remaining uncovered risk is real-provider timing outside the deterministic Claude/OpenCode adapter tests.

Review focus

• The framework-title versus app-generated fallback race and usage accounting.
• First-turn identity preservation when a framework title arrives after later turns.
• Session title precedence and ordered persistence under concurrent saves.
• Maintenance cost of the version-pinned Claude ACP patch.