fix(wiki-compose): hydrate UI from PATCH resume output

[cursor]

Bug and impact

Wiki Compose P2 (#950 / PR #959) could complete the orchestrator on the server while the split-screen UI showed an empty draft. After approving the outline, PATCH /resume runs draft_sections + completed synchronously and returns output.completion, but useWikiComposeSession only updated status and skipped POST /run when status was completed, so completedMarkdown and section bodies never reached the editor.

The same pattern affected Brief/Research submits: the hook discarded PATCH /resume output and called POST /run with fresh graph input on an interrupted checkpoint, which LangGraph does not support (resume requires Command({ resume })).

Root cause

• Non-streaming resume returns graph state in JSON (__interrupt__ or completion), not over SSE.
• Client assumed a follow-up POST /run would always hydrate the next phase; E2E mocks masked this by always serving draft tokens from /run.

Fix

• reduceResumeOutput() applies interrupt payloads and final completion from resume output.
• Submit handlers only call streamRun when resume output did not hydrate UI state.
• start() only calls POST /run for pending/failed sessions (not interrupted reloads).
• WikiComposePage replaces the URL with /compose/:sessionId after session create so refresh reopens the same row.
• Tests lock outline completion and research interrupt hydration.

Validation

• npx vitest run src/hooks/useWikiComposeSession.test.ts (5 tests, pass)

Triggered by automation review of PR #959.