refactor(hosts): isolate scheduler guides by OS

[xnne-bot]

📝 Pull Request Summary

Split the Agent-facing bridging scheduler guides by OS for Claude Code, Cursor, and Hermes, so each agent sees only the registration flow that applies to its current platform.

Closes #626.

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✅ What does this PR do?

• Adds BRIDGING_TASK.windows.md and BRIDGING_TASK.unix.md for the three OS-scheduled hosts.
• Makes docs task select the platform-specific resource, including its remote-doc URL and cache key.
• Keeps the existing Windows Task Scheduler and Unix cron/launchd implementations unchanged.
• Preserves native-scheduler and generic host behavior; generic only updates a link to the renamed Claude Code Unix guide.
• Adds focused Windows/Linux/macOS selection, platform-isolation, prompt-parity, cron-line-length, and wrapper-marker coverage.

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🤔 Why is this change needed?

The combined guides exposed both complete registration paths at once. Windows agents saw cron, launchd, bridge.sh, and Unix PATH setup, while Unix agents saw Task Scheduler, S4U, PowerShell, and schedule install. This widened the decision surface and made selecting an inapplicable registration path more likely.

Related issue: #626.

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🔍 Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / cleanup
• Other (please explain)

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✅ PR Quality Checklist

• PR title follows an allowed format (for example feat:, fix:, docs:, memory base:)
• Changes are limited in scope and easy to review
• Documentation updated where applicable
• No breaking changes (or clearly documented)
• Related issues or discussions linked

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📌 Optional

• Screenshots or examples added (if applicable)
• Edge cases considered
• Follow-up tasks mentioned

Follow-ups remain intentionally out of scope: pipeline-prompt deduplication (#628) and wrapper-contract discussion (#629).

Verification:

• uv run pytest tests/test_scheduling_windows.py tests/test_bridging_self_sessions.py tests/test_cursor_self_sessions.py tests/test_events.py -k \"scheduling_windows or bridging_self_sessions or cursor_self_sessions or only_the_install_guide_reports_an_attempt\" — 63 passed
• uv run ruff check ... — passed
• uv run mypy ... — passed
• Built wheel contains all six platform guide resources; all three Windows docs task CLI smoke tests passed.

🤖 Generated with Claude Code

[MrXnneHang]

not ready yet.

这个 PR 大概率会沉底到 codex OS scheduler 完成后才接着写。