feat(hackernews): add new, best, ask, show, jobs, search, user commands

[Astro-Han]

Description

Expand HackerNews from 1 command to 8, covering all major HN use cases. All commands use public APIs (strategy: public, browser: false) — no login or browser required.

Command	API	Description
hackernews new	Firebase newstories.json	Newest stories
hackernews best	Firebase beststories.json	Best stories
hackernews ask	Firebase askstories.json	Ask HN posts
hackernews show	Firebase showstories.json	Show HN posts
hackernews jobs	Firebase jobstories.json	Job postings
hackernews search <query>	Algolia Search API	Full-text search with --sort relevance/date
hackernews user <username>	Firebase user/{id}.json	User profile (karma, created date, about)

Also improves existing top command with deleted/dead item filtering and dynamic pre-fetch limit.

Example output

$ opencli hackernews search "typescript" --limit 3
┌──────┬──────────────────────────────────┬───────┬────────┬──────────┐
│ Rank │ Title                            │ Score │ Author │ Comments │
├──────┼──────────────────────────────────┼───────┼────────┼──────────┤
│ 1    │ TypeScript types can run DOOM    │ 1328  │ franky │ 360      │
│ 2    │ Why Discord is switching to Rust │ 1582  │ Sikul  │ 642      │
│ 3    │ TypeScript is more popular...    │ 876   │ hk__2  │ 544      │
└──────┴──────────────────────────────────┴───────┴────────┴──────────┘

$ opencli hackernews user pg
┌──────────┬────────┬────────────┬─────────────┐
│ Username │ Karma  │ Created    │ About       │
├──────────┼────────┼────────────┼─────────────┤
│ pg       │ 157316 │ 2006-10-09 │ Bug fixer.  │
└──────────┴────────┴────────────┴─────────────┘

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

Testing

• All 7 new commands verified with npm run dev (returns valid JSON)
• 9 E2E tests pass in tests/e2e/public-commands.test.ts (2 existing + 7 new)
• npm run typecheck passes
• npm run build — 300 manifest entries (293 → 300)

Documentation

• Updated README.md hackernews command table
• Updated README.zh-CN.md hackernews command table
• Updated docs/adapters/browser/hackernews.md with all 8 commands
• Updated docs/adapters/index.md command list