[IR-P0][WS1] Phase 0 contract freeze (epic)

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Problem statement

Phase 0 needs a single controlling issue that defines completion criteria and links all contract-freeze deliverables.

Intended invariant

No implementation work proceeds without approved IR contracts and executable invariant criteria.

Scope boundaries

• Coordinates Phase 0 only
• Tracks deliverable issues and gate evidence
• Does not implement runtime behavior changes

Deliverable checklist

• IR contract RFC approved
• Invariant spec approved
• Golden vectors and CI harness skeleton merged
• Exit gate evidence linked
• Child issues include required migration/docs impact assessments

Validation plan

Phase 0 closes only when each child issue is Done and gate evidence is attached.

Rollback/failure mode

If scope expands beyond contract freeze, split into a Phase 1+ issue and keep this epic focused.

Roadmap reference

Roadmap reference: docs/plans/2026-06-19-001-ir-first-roadmap.md (Phase 0)

Migration impact

none - Epic coordination only; no direct user-facing behavior changes.

Documentation impact

none - Epic tracking issue; documentation updates are owned by child delivery issues.

Sync status

Synced with roadmap: 2026-06-19

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Roadmap sync update (2026-06-19): IR work branch policy is now explicit -- implementation branches must be created from feat/ir-first and PRs must target feat/ir-first. main promotion is deferred until the full IR program is complete and release-ready.

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Epic sync update: milestone IR-P0 created and assigned to #71-#74. Phase 0 deliverable artifacts are now present on branch feat/ir-first; roadmap and migration-guide synchronization updated in the same work session.

[0x054]

Phase 0 epic complete. Child issues #72, #73, and #74 are now closed.

Merged evidence: PR #75 #75
Roadmap sync: docs/plans/2026-06-19-001-ir-first-roadmap.md updated to Phase 0 complete.