refactor(routes): share the isStatusLabel guard

[joryirving]

Summary

• Hoist the duplicated isStatusLabel type guard (identical copies in issues/status/route.ts and issues/move/route.ts) to @/types, next to STATUS_LABELS/StatusLabel, and import it in both.

Verification

• tsc → 0; eslint → clean; vitest status + move + types → 52 passing.

Closes #508 · part of #498

[its-saffron]

AI Automated Review

Full PR review.

Analysis engine: MiniMax-M2.7@https://litellm.jory.dev/v1 (anthropic) — routed smart (risk match: public_route_changes)

Recommendation: Approve

This is a clean, low-risk refactor that extracts a duplicated isStatusLabel type guard into a shared location.

Change-by-Change Findings

src/types/index.ts (+5 lines)

• Added the isStatusLabel type guard adjacent to STATUS_LABELS/StatusLabel — appropriate colocation per issue PR 508 guidance.
• The function body is identical to the two local copies removed; only location changes.

src/app/api/issues/move/route.ts (−5 / +1 lines)

• Replaced import { STATUS_LABELS, StatusLabel } with import { STATUS_LABELS, isStatusLabel }.
• Removed the now-inlined local function.
• Auth: authorizeRequest / auth.authorized check remains unchanged.

src/app/api/issues/status/route.ts (−5 / +1 lines)

• Added isStatusLabel to the existing import.
• Removed the now-inlined local function.
• Auth: authorizeRequest / auth.authorized check remains unchanged.

Required Checks

Check	Result
Verify route access controls are in place	✅ Verified — both move/route.ts and status/route.ts retain their authorizeRequest / auth.authorized gate. The refactor moved only the type guard; zero auth logic was altered.
Check for unintended public endpoints	✅ Verified — no new route handlers, no new HTTP method exposures, no middleware changes. Only a pure-code-movement refactor of an internal type guard.

Standards Compliance

• No agent-specific names introduced.
• No secrets committed.
• No deviations from AGENTS.md conventions.
• CI checks: Lint ✅, Typecheck ✅, Build ✅, Tests ✅, Docker Build ✅ (all passing).

Linked Issue Fit

PR 508 asked to extract isStatusLabel + optionally a mutateStatusLabels helper. This PR fully delivers the isStatusLabel extraction. The "optionally" clause means the second helper was not required; the issue is partially addressed and on-track for completion.

Evidence Provider / Tool Harness Findings

None applicable — no evidence providers configured, no tool calls issued.

Unknowns / Needs Verification

None.