refactor(architecture): tighten desktop boundaries

[hiqiancheng]

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For code changes, this PR must link the related issue or RFC in the section below.

Summary

Tightens the desktop frontend architecture boundaries for RFC #434.

• Moves stable cross-layer DTOs into apps/desktop/src/contracts while keeping runtime policy in application or services.

• Splits popup definitions so manifest/layout metadata is contract-owned and Vue component binding stays in PopupView.

• Extracts attachment storage, HTTP fetch, database runtime, data backup, and provider config policy out of overloaded service internals.

• Strengthens import-boundary tests so baseline violations and unexpected dependency cycles are caught explicitly.

• Adds direct boundary characterization tests for popup manifest/component sync, DatabaseRuntimeService, HttpService Tauri fetch wrapping, and DataManagementService backup failure semantics.

• Strengthens desktop E2E smoke coverage for startup, quick search results, model dropdown popup, session history popup, settings persistence, and settings section navigation.

• Adds reusable E2E window helpers that identify Tauri windows by in-page state and include diagnostic snapshots on multi-window failures.

• Adds popup-window smoke coverage for both registered popup manifests and the Vue component binding path.

• Skips remote model metadata bootstrap in E2E mode so UI critical-path smoke tests are not gated on network metadata refresh.
  User-facing impact: no intended behavior change. This is an architecture-boundary refactor aimed at reducing future cross-layer coupling.

Related issue or RFC

Link the issue or RFC:

• Related to [RFC]: Refactor desktop frontend architecture boundaries #434

For code changes, link the tracking issue. Only documentation wording, link fixes, or comment-only cleanups may skip the issue-first flow.

AI assistance disclosure

If AI tools materially assisted this contribution, disclose that here or point to the relevant commit trailer.

• Tool(s) used: Codex; Brooks-lint subagent (Volta) for architecture and test-quality review.
• Scope of assistance: implementation planning, code changes, boundary-test hardening, and review of architecture/test-suite risks.
• Human review or rewrite performed: changes were reviewed during preparation; maintainers should still review the full boundary model and risk areas.
• Architecture or boundary impact: yes; this PR moves shared contracts and runtime policy across desktop frontend layers under accepted RFC [RFC]: Refactor desktop frontend architecture boundaries #434.

Testing evidence

List the commands you ran and the results you observed.

• pnpm --filter @touchai/desktop test:e2e - passed locally; startup, quick search, model dropdown popup, session history popup, and settings smoke specs ran together with 5 passing.
• pnpm --filter @touchai/desktop test:unit -- tests/i18n/main-bootstrap.test.ts - passed; Vitest executed the desktop frontend suite: 133 files / 771 tests.
• pnpm --filter @touchai/desktop test:typecheck - passed.
• pnpm --filter @touchai/desktop type:check - passed.
• pnpm --filter @touchai/desktop lint:check - passed with 20 existing warnings and 0 errors.
• pnpm --filter @touchai/desktop format:check - passed.
• Commit hook verification also passed pnpm --filter @touchai/desktop check:rust, pnpm --filter @touchai/desktop type:check, staged ESLint, and staged Prettier; Rust emitted 2 existing unused warnings in src/core/search/manager.rs.
• Earlier focused tests passed for architecture import boundaries, popup manifest/component sync, DatabaseRuntimeService, HttpService Tauri fetch wrapping, DataManagementService backup failure semantics, setting-tool i18n, AgentService error i18n, useAgent i18n, database backup i18n, and NativeService coverage touched by this refactor.
• pnpm test:pr - check and test:unit passed, then test:rust stopped when build.rs timed out downloading https://github.com/rtk-ai/rtk/releases/download/v0.40.0/rtk-x86_64-pc-windows-msvc.zip with Windows socket error 10060.
• Local test:rust retry could not proceed because this machine has C: full, no E:/G: drives, and L:\TouchAI cannot be created (The request is not supported). CI should provide the first complete Rust proof for this PR.

Did you follow TDD (test-first) for feature and fix work? Strongly recommended. See docs/testing/testing.md.

pnpm test:pr

Risk notes

• AgentService, runtime, MCP, or schema impact: touches AgentService runtime boundaries and shared contracts; no MCP behavior change intended.
• database baseline or migration impact: no schema, migration, or baseline changes intended.
• release or packaging impact: only test timeout handling for Velopack release-asset normalization was adjusted; no packaging behavior change intended.

Screenshots or recordings

Not applicable; no intended UI behavior change.

Checklist

• The PR title follows Conventional Commits and is valid for squash merge.
• This PR is either ready for review or explicitly marked as a Draft PR.
• I did not use [WIP] or similar title prefixes.
• If AI materially assisted this PR, I disclosed the tools and scope and I personally reviewed every affected change.
• I can explain the why, what, and how of this change without relying on an AI tool.
• If this touches AgentService, runtime, MCP, or schema boundaries, there is an accepted RFC.
• If this changes architecture or adds a new cross-boundary abstraction, there is an accepted RFC.
• I ran pnpm test:pr for this code PR, or this is a docs-only change.
• If I changed Rust behavior or tests, I reviewed pnpm test:coverage:rust or relied on CI coverage evidence.
• If I changed desktop startup/window/search/popup/settings/E2E paths, I ran pnpm test:e2e locally or documented why CI is the first valid proof.
• I added tests or explained why tests are not appropriate.
• I updated docs when behavior changed.

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