Add 1Point3Acres adapter commands

[KehaoC]

Summary

Adds 1Point3Acres adapter coverage for #676.

1Point3Acres is a particularly valuable information source for international students, including Chinese students studying abroad. Many students and early-career professionals check it frequently for admissions, job search, workplace, and overseas life discussions.

• Add public YAML commands for forum discovery and thread lists:
  • 1point3acres forums
  • 1point3acres hot
  • 1point3acres threads
• Add browser-backed commands for logged-in forum access:
  • 1point3acres posts
  • 1point3acres search
• Document the adapter in README and adapter docs.

Validation

• npm run build
• npm run start -- 1point3acres forums --limit 5
• npm run start -- 1point3acres threads --limit 3
• npm run start -- 1point3acres posts 1171818 --limit 1 -f yaml --verbose
• npm run start -- 1point3acres search 面经 --limit 1 -f yaml --verbose

Notes

The public commands ran successfully against the 1Point3Acres API. The posts command uses the logged-in browser session to parse the thread page because the posts API rejects the earlier request shape with HTTP 400. The search command checks the API first and reports a clear account-permission error when the logged-in 1Point3Acres user group cannot use site search.

Closes #676