feat(app): support v1 and v2 servers

[Brendonovich]

Summary

• detect server protocol capabilities and route app operations through V1 or V2 clients
• normalize session, message, project, MCP, terminal, and diff data across both protocol versions
• vendor the self-contained V2 promise client while continuing to resolve the legacy SDK from the workspace
• expand unit and E2E coverage for dual-server behavior

Validation

• bun typecheck in packages/app
• bun typecheck in packages/session-ui
• bun typecheck in packages/desktop
• bun run typecheck:e2e in packages/app
• 116 focused app compatibility tests
• 76 session UI tests

The complete app unit suite reports 659 passing tests and one unrelated existing Arabic i18n parity failure.

[Brendonovich]

Superseded by the reviewable stack beginning with #38467 and ending with #38463. The cumulative tree of the stack is identical to this PR.