Update migration-from-legacy.md to implemented status#

Problem#

The migration document described the shell-to-agent-core migration as in-progress and was missing documentation for the refine phase PM workflow, hook behavior, and router routing.

Task / Link#

Closes #46

Changes#

• Set status: implemented and last-updated: 2026-03-16 in YAML frontmatter
• Document refine phase conversational PM Q&A workflow and PhaseHooksService post-hook behavior (removes in-refinement label, moves to AgentQueue; no refined label added)
• Document issue_comment router routing: routes to refine phase if in-refinement label present, otherwise to directive handling
• Add in-refinement to Labels Kept by TLA; move awaiting-plan-approval to Labels Deprecated by TLA
• Replace draft/in-progress coexistence language with historical framing
• Add migration completion note confirming all 17 WAL issues merged as of 2026-03-16

Notes#

awaiting-plan-approval was previously listed under Labels Kept by TLA; moved to deprecated as it is replaced by the /agent approve directive in TLA.

Testing#

• Document-only change; verified against acceptance criteria in plan.md
• No references to refined label remain outside legacy labels table