fix(browser): harden multi-tab routing and target isolation

[freemandealer]

Description

Fix browser multi-tab concurrency and target isolation on top of the latest main without carrying the earlier network-detail-cache commit.

• make daemon command ids collision-resistant and retry duplicate pending ids
• add validated browser tab list/new/select/close flows with persisted default targets
• keep untargeted browser commands on the default tab unless tab select changes it
• document tab targeting and add unit, extension, and e2e coverage for concurrent multi-tab execution

Related issue:

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🌐 New site adapter
• 📝 Documentation
• ♻️ Refactor
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Documentation (if adding/modifying an adapter)

• Added doc page under docs/adapters/ (if new adapter)
• Updated docs/adapters/index.md table (if new adapter)
• Updated sidebar in docs/.vitepress/config.mts (if new adapter)
• Updated README.md / README.zh-CN.md when command discoverability changed
• Used positional args for the command's primary subject unless a named flag is clearly better
• Normalized expected adapter failures to CliError subclasses instead of raw Error

Screenshots / Output

npx vitest run --project unit src/cli.test.ts src/browser/page.test.ts src/browser/daemon-client.test.ts
# Test Files  3 passed (3)
# Tests  42 passed (42)

npx vitest run --project extension extension/src/background.test.ts
# Test Files  1 passed (1)
# Tests  18 passed (18)

npx vitest run --project e2e tests/e2e/browser-tabs.test.ts
# Test Files  1 passed (1)
# Tests  4 passed (4)