feat(protocol): add planning journal envelopes

[glittercowboy]

Summary

• add planningEvent and planningEventAck message contracts
• register envelope parsing for both message types
• document source sequencing, idempotency, payload, and ack behavior

Verification

• go test ./...

Dependency order

Merge this PR before bumping protocol-go consumers in daemon or cloud relay. After merge, tag protocol/v0.5.0.

Summary by CodeRabbit

• New Features
  • Added planning event messaging to the relay for tracking distributed operations
  • Planning events support idempotent delivery with causation tracking and correlation identifiers
  • Relay acknowledges event acceptance, indicating successful persistence or idempotent replay with optional error details

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR introduces two new message types for planning journal workflows: planningEvent for append-only events emitted by source runtimes with identity, ordering, correlation, and timing metadata; and planningEventAck for relay acknowledgements indicating event persistence or idempotent replay status.

Changes

Cohort / File(s)	Summary
Protocol Documentation PROTOCOL.md	Defines two new message types: planningEvent with identity, ordering (sourceSeq), idempotency (idempotencyKey, causationId), timing (occurredAt), and structured data fields; and planningEventAck for relay acknowledgement with acceptance status and optional error details.
Message Type Definitions messages.go	Introduces MsgTypePlanningEvent and MsgTypePlanningEventAck message type constants, plus corresponding struct types PlanningEvent and PlanningEventAck with full field schemas including identifiers, sequencing, and payload/evidence metadata.
Envelope Parsing envelope.go	Updates payloadForType function to recognize the two new message types and return their respective payload struct instances instead of defaulting to unknown message type error.
Unit Tests messages_test.go	Adds round-trip marshal/parse tests validating that PlanningEvent and PlanningEventAck preserve key fields (identity, sequencing, acceptance status) through JSON serialization and envelope parsing with proper type assertions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add context compaction protocol messages #21: Adds new wire message types and payload structs, updating the same envelope payloadForType switch to recognize additional message types.

Poem

🐰 Events now plan with careful grace,
Through relay's warm and nested space,
Each ack confirms the journey's trace,
With source and seq in their right place! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(protocol): add planning journal envelopes' accurately describes the main change: adding two new message types (planningEvent and planningEventAck) to the protocol with supporting documentation and envelope parsing.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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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 codex/planning-journal-protocol

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