refactor: extract CooldownSynthesisManager from CooldownSession (Wave 2C, #375)

[cmbays]

Summary

• Extract 13 synthesis IO methods (~230L) into dedicated CooldownSynthesisManager class
• CooldownSession: 965 → 744 lines (-23%)
• Constructor DI with CooldownSynthesisDeps interface
• loadBridgeRunIdsByBetId wired as deps function (keeps BridgeRunSyncer out of synthesis deps)
• 5 proposal types: new-learning, update-learning, promote, archive, methodology-recommendation

Quality

• 23 BDD scenarios (CPO + CQO audited)
• 21 unit tests
• CRAP < 8 (worst 4.6)
• ArchUnit 14/15 (CycleManager LCOM4 pre-existing)
• Mutation 81.58% overall, 96.88% covered (threshold 70%)

Decomposition Progress

Wave	Service	Lines	PR
1A	BridgeRunSyncer	195L	#396
1B	CooldownBeltComputer	85L	#397
2A	CooldownFollowUpRunner	124L	#398
2B	CooldownDiaryWriter	191L	#399
2C	CooldownSynthesisManager	273L	this PR
3A	Final wiring + quality gates	—	next

Part of #375

Summary by CodeRabbit

• Refactor
  • Reorganized internal synthesis operations in cycle management for improved maintainability and code clarity.
• Tests
  • Added comprehensive scenario-based and unit test coverage for synthesis management.

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Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

A CooldownSynthesisManager class was extracted to encapsulate synthesis file I/O and proposal application logic previously embedded in CooldownSession. The manager coordinates synthesis input writing, stale file cleanup, bridge-run ID resolution, and result reading with knowledge-store mutations. CooldownSession now delegates these responsibilities. Comprehensive BDD and unit test coverage was added alongside feature specifications.

Changes

Cohort / File(s)	Summary
New CooldownSynthesisManager Implementation src/features/cycle-management/cooldown-synthesis-manager.ts	Added dependency-injected manager class with writeInput() and readAndApplyResults() public methods. Orchestrates synthesis JSON file I/O, stale input cleanup, bridge-run ID mapping, knowledge-store observation querying, and proposal application (new-learning, update-learning with confidence clamping, promote, archive, methodology-recommendation logging). Includes error handling with warning logs that continue processing on failures.
Test Coverage for CooldownSynthesisManager src/features/cycle-management/cooldown-synthesis-manager.feature, src/features/cycle-management/cooldown-synthesis-manager.steps.ts, src/features/cycle-management/cooldown-synthesis-manager.test.ts	Added Gherkin feature file with behavioral scenarios. BDD step definitions and unit tests exercise input writing (with stale cleanup, run-ID resolution, learnings embedding, missing directories), result reading/parsing, proposal filtering and application per type, and error resilience (observation read failures, parse failures, proposal application failures).
CooldownSession Refactoring src/features/cycle-management/cooldown-session.ts	Extracted inline synthesis orchestration (filesystem operations, JSON handling, synthesis result reading, proposal application) into CooldownSynthesisManager. Updated prepare() to call synthesisManager.writeInput() and complete() to call synthesisManager.readAndApplyResults(). Removed direct helper imports and related utility functions.
Build & Setup Configuration src/acceptance/setup.ts, stryker.config.mjs	Added import for cooldown-synthesis-manager BDD steps in acceptance setup. Extended Stryker mutation testing scope to include the new manager class.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• test: mutation hardening cycle — 72.19% to 78.14% (+5.95pp) #386: Adds unit tests exercising cooldown-session's synthesis and observation/proposal-application paths, directly testing the logic being refactored into CooldownSynthesisManager
• refactor: extract BridgeRunSyncer from CooldownSession (Wave 1A) #396: Extracts and wires BridgeRunSyncer providing loadBridgeRunIdsByBetId, which is a dependency callback injected into the new CooldownSynthesisManager
• refactor: extract CooldownDiaryWriter from CooldownSession (Wave 2B, #375) #399: Applies the same refactoring pattern to CooldownSession by extracting functionality into a new collaborator (CooldownDiaryWriter), parallel to this PR's extraction of synthesis orchestration

Poem

🐰 A synthesis so clean and bright,
Manager takes the heavy load,
Session delegates with delight,
Proposals marching down the road!
Error-handling hops with care,
Tests ensure the way is fair. ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: extraction of CooldownSynthesisManager from CooldownSession, with relevant context (Wave 2C and issue reference).

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch wave-2c-cooldown-synthesis-manager

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