fix(summon-title): defer title set until after workspace initialization

Setting the title in the HTTP /chat route BEFORE the turn started pre-created
the conversation meta, which made the orchestrator's getConversationMeta ===
null newness check falsely report an EXISTING conversation. As a result
ensureWorkspace / setWorkspaceId / the first-turn systemPromptService.construct
were ALL skipped for summoned conversations with a title — leaving them with no
assigned workspace and breaking downstream cwd resolution + system-prompt init.

Fix: the title is no longer set in the route. It is threaded through
StartTurnInput -> handleMessage -> startTurn -> runTurnDetached and persisted
via setConversationTitle INSIDE workspaceSetupPromise, AFTER the newness check
+ workspace assignment (so init still fires for new conversations) and BEFORE
the first message append (so the append's auto-derived title does not overwrite
it). The title set is best-effort: a failure is logged but does not break the
turn (the workspace setup already succeeded).

The /chat route now forwards title into the orchestrator input instead of
calling setConversationTitle itself.

Tests:
- app.test.ts: route tests rewritten to assert the route forwards title to the
  orchestrator and does NOT call setConversationTitle itself.
- orchestrator.test.ts: 5 new regression tests, including the critical 'titled
  new conversation still gets workspace assigned + system-prompt constructed +
  title set', an ordering test (title set after getMeta/ensureWorkspace/
  setWorkspaceId), and a resilience test (turn completes if setConversationTitle
  throws).

Verification: typecheck EXIT 0; test 2026 passed | 6 skipped | 0 failed;
check EXIT 0 (12 pre-existing warnings in untouched files).

0 files changed, 0 insertions, 0 deletions