Nano: support Supervisor planning, specification, and archive sessions

[RomanEmreis]

Planned PR 17 of 18. Phase: N5 roles. Later release.

Series overview and full PR index: #73.

What problem does this solve?

Interactive nano can later replace an external Supervisor for planning/spec work, but enabling a UI alone does not supply the required role-specific tools and authorization.

Proposed solution

• Implement the Supervisor adapter/profile under src/nano/ using the same engine and narrow existing registration hooks.
• Connect taskless planning/task-definition and specification operations natively through existing enqueue/create-spec behavior.
• Add the distinct spec-archive profile using the existing Outcome authoring/approval/archive flow; preserve the required human approval boundary.
• Expose tools by actual session mode: taskless definition tools and archive tools are not automatically available to task-scoped sessions.
• Maintain scoped instructions, graph/memory access, model/version/config behavior, and native integration without loopback MCP.

Acceptance criteria

• HQ planning/task/spec/archive entry points can launch the matching native mode with correct tool visibility and guards.
• Tests cover role mismatch, mode-scoped tool denial, duplicate/invalid task creation, specification validation, and human approval handling.
• Archive preserves existing provenance/source policy and best-effort memory refresh; a refresh failure does not undo a successful archive.
• Outcome content is authored only through the existing approved workflow, not by session compaction or arbitrary tools.
• External Supervisor adapters and native Executor behavior remain unchanged.
• Relevant tests plus cargo fmt --check, cargo clippy -- -D warnings, and cargo test pass; new feature combinations get explicit coverage where applicable.

Impact on workflow (if any)

Adds native Supervisor participation in existing planning/spec/archive workflows without introducing task states or relaxing approval semantics.

Dependencies

• Depends on Nano: add an interactive conversation view to Ferrus HQ #86: Nano: add an interactive conversation view to Ferrus HQ.

Implementation boundaries

Reviewer/Consultant execution, automatic task decomposition, autonomous approval of specs/Outcomes, and a second orchestrator are outside this PR.

Keep new harness implementation in src/nano/. Reuse existing Ferrus modules in place and make only the small integration changes this PR needs. Introduce src/shared/ only for an implementation actually shared by HQ and nano; preserve the existing lifecycle and graph/memory domain boundaries.

Code entry points (existing or proposed): src/nano/{agent,ferrus,instructions}.rs, existing enqueue_task/create_spec/archive_spec operations, HQ mode routing.