fix: Standardize migration guide references to canonical path

[ashleyshaw]

Description

Standardize all references to the migration guide to use the canonical path location (/docs/MIGRATION.md) instead of root-level paths, ensuring compliance with repository governance standards.

Changes

Updated the following governance files to reference the canonical migration guide location:

1. AGENTS.md (2 references)

   • Line 33: Updated mapping reference in core instructions section
   • Line 95: Updated table entry for migration guide reference

2. .github/README.md (1 reference)

   • Line 391: Updated link to canonical migration guide location

3. .github/instructions/.archive/README.md (3 references)

   • Line 26: Updated status marker for superseded migration guide
   • Line 33: Updated canonical version reference
   • Line 110: Updated instructions for accessing archived files

Rationale

Following the repository standards documented in CLAUDE.md and .github/README.md, all governance documentation should reference the canonical path for consolidated files. The migration guide exists at /docs/MIGRATION.md as the single source of truth for migration information.

Files Changed

• AGENTS.md
• .github/README.md
• .github/instructions/.archive/README.md

Acceptance Criteria

• All migration guide references point to /docs/MIGRATION.md
• Archive documentation correctly indicates canonical location
• No references to root-level MIGRATION_GUIDE.md remain
• Governance files comply with repository standards
• PR fix: CodeRabbit schema validation and migration guide references #785 passes CI checks

Standards Reference

• CLAUDE.md — Repository boundaries and file organization
• .github/README.md — Governance file standards
• docs/MIGRATION.md — Canonical migration guide

Definition of Ready (DoR)

• Task/goal described and scoped
• Confirms it does not fit the Code Refactor or Maintenance templates
• Acceptance criteria listed
• Estimate added (if applicable)

Definition of Done (DoD)

• Affected files, labels, or settings updated and documented
• PR uses correct branch prefix (chore/)
• Approved by at least one maintainer

[linear-code]

LS-928