update: v0.3

[lightbulb128]

Added

• Multi-session chat: session management and transcript handling so a
  conversation can span multiple chat sessions, with single-session history
  loading that is context-aware (#63).
• Conversation re-connect: resume interrupted conversations with unit-test
  coverage for the reconnect path.
• Project deliverables: publish files produced during chat sessions as
  project deliverables. Adds the t_project_deliverable store, deliverable
  proto/API, and richer project detail/query responses (#69).
• Experience improvements: playbook management, per-turn learned
  experience tuning, and display fixes (restored from #59).

Changed

• Context management: reintegrate tool-context compaction to keep long
  conversations within the model's context budget.
• Sync chat construction and plan/message handling with upstream.

Removed

• Removed the test-cases-rewrite skill and its backend wiring.

Fixed

• Core: repair cancelled tool-call history.
• Frontend: read agent avatar from agentIconUrl, pass conversationId to
  /conversation/plan and plan/cancel, redirect bare / to /digital-worker
  with deliverable fileUri fallback, treat roles as scoped objects with an
  optional project iconUrl, and commit vendored config base files (#90, #93,
  #96, #97, #98).
• Restore the vendored frontend build-from-source pipeline (#83).