[MAINTENANCE] Consolidate duplicated OS-scheduled bridging pipeline prompts

Context

The OS-scheduled bridging guides for Claude Code, Cursor, and Hermes each carry a full copy of the prepare → self-evolve → commit pipeline prompt. The Python builder at src/memu/hosts/scheduling/prompt.py is also a canonical copy; current tests deliberately assert that the guide snippets match it.

This duplication is expected today and is not a reported correctness bug. The existing equality tests make drift visible, but maintaining multiple copies remains a long-term cost.

Discussion target

Decide whether a future change should make one source generate or parameterize the host-specific prompt artifacts while preserving:

• host-specific binary/base-dir/session-dir substitutions;
• agent-readable Unix setup instructions;
• packaged-guide, remote-guide, and cached-guide behavior; and
• tests that fail on actual prompt drift.

Out of scope

• Any change to pipeline behavior or the current prompt wording.
• Windows/Unix scheduler registration or lifecycle.
• Wrapper generation or parity.
• The platform-specific guide isolation tracked in #626.

Done when

There is an agreed implementation direction and migration/test plan. Implementation can follow in a separate PR.