fix: harvest session state before /clear and /compact

[qozle]

Summary

• /clear and /compact destroy conversation context without triggering SessionEnd, so WorkCompletionLearning, RelationshipMemory, and progress snapshots are silently lost
• Adds PreContextReset.hook.ts — a UserPromptSubmit hook that detects /clear and /compact and runs a lightweight harvest before context is destroyed
• Registered first in the UserPromptSubmit hook chain so it runs before other hooks

What it harvests

1. Work completion learning — captures active work state and ISC progress to MEMORY/LEARNING/
2. Relationship notes — appends session interaction notes to MEMORY/RELATIONSHIP/
3. Progress snapshot — annotates active progress files with a context-reset marker
4. Rating signal marker — marks the reset point in ratings.jsonl so downstream analysis knows context changed

Does NOT run cleanup (tab reset, state deletion) since the session continues after both commands.

Performance

• Non-matching prompts (99% of traffic): <5ms fast exit
• Matching prompts: <100ms — all disk I/O, no inference calls

Test plan

• Run with non-reset prompt — verify silent fast exit, no side effects
• Run with /clear — verify learning file created, relationship note appended, rating marker written
• Run with /compact — same verification
• Verify no active work state handles gracefully (no crash, no empty files)

Closes #1043