feat(linux-do): add linux.do adapter with 6 commands

[Astro-Han]

Summary

Closes #43. Adds linux.do (Discourse-based Chinese tech forum) support with 6 YAML pipeline commands:

• hot - trending topics with period filter (all/daily/weekly/monthly/yearly)
• latest - newest topics
• categories - list all categories (with slug/id for category command)
• category - browse topics within a specific category
• topic - post details with replies (first page)
• search - search topics by keyword

All commands use navigate + evaluate pattern with cookie auth (browser: true), since linux.do enforces login_required on all API endpoints.

Security

• User string inputs (keyword, slug, period) sanitized via | json template filter + encodeURIComponent
• Integer inputs (id, limit) type-enforced by framework before template expansion

HTML handling (topic command)

• Block tags (<p>, <br>, <div>, etc.) converted to spaces
• Named entities (&, <, etc.) decoded
• Numeric entities (decimal ' and hex ') decoded via String.fromCodePoint with try-catch guard
• Content truncated to 200 chars

Files changed

• src/clis/linux-do/ - 6 YAML adapter files
• tests/e2e/browser-auth.test.ts - 6 graceful-failure test cases

Test plan

• npm run build - 110 entries (30 YAML, 80 TS), includes 6 new linux-do commands
• npm run typecheck - passes
• npx vitest run src/ - 200 unit tests pass
• opencli linux-do --help - all 6 subcommands registered
• 4 rounds of multi-model code review (crosscheck)
• Live data verification (requires linux.do login - invite-only registration)