feat: add human-agent work continuity

[Teingi]

Which issue or RFC does this PR close?

Closes #1224.

This PR introduces RFC 1223: Human-Agent Work Continuity.

Rationale for this change

PowerContext already has Prepared Handoffs, immutable committed revisions, evidence checks, Continue semantics, and Handoff Report. The missing layer is a small user-facing work-continuity loop that distinguishes new delegation from transfer of work already in progress and records whether the receiver understood the handoff and what happened afterward.

This keeps human-to-human, human-to-Agent, and Agent-to-Agent transfer on one evidence-bearing Handoff core without introducing a parallel task database, workflow engine, or mandatory session-end hook.

What changes are included in this PR?

• Add a bilingual RFC for the shared Work Contract -> Handoff -> Acknowledge -> Task Outcome loop.
• Add typed Source-backed Work Contract, Current Work Handoff, Handoff Receipt, and Task Outcome records.
• Add four high-level OpenAPI operations and generated transport bindings:
  • create_work_contract
  • handoff_current_work
  • acknowledge_handoff
  • record_task_outcome
• Expose the operations through the Runtime, HTTP Server, Python Client, and MCP.
• Require exact evidence for verified claims and prevent accepted acknowledgements when Handoff evidence is unavailable.
• Keep Handoff commit explicit and preserve existing compare-and-swap and immutable-revision behavior.
• Preserve metadata.kind="task-outcome" so outcomes remain compatible with reviewed Experience incubation.
• Update the Codex project-context skill and bilingual interface documentation.
• Add focused model, Runtime, API contract, SDK, MCP, and SQLite end-to-end coverage.

Are there any user-facing changes?

Yes. Integrations can use four new /v1/work/... endpoints, matching Python Client methods, and MCP tools to create a delegation baseline, prepare current work for transfer, acknowledge a resolved Handoff, and record a completion-aware result.

The change is additive. Existing Handoff, Memory, PreparedContext, Experience Review, and Report behavior remains available. Work records are untrusted input or observation and do not grant tool, network, credential, or execution authority. Persisting a Handoff milestone still requires explicit commit_handoff.

How was this change tested?

• make check
• make test — 439 passed, 7 environment-dependent tests skipped
• make contract-test — 25 passed
• make docs-test
• make build

The SQLite Server end-to-end test exercises Work Contract creation, temporary and committed Handoff acknowledgement, and Task Outcome recording. Live OceanBase validation was not performed.

AI usage statement

Codex with OpenAI GPT-5 was used to analyze the existing contracts, draft the bilingual RFC, implement the feature, add tests, and run validation. The resulting code and documentation were reviewed against the repository guidelines and generated API contract.