refactor(coordination): make managed Leads orchestration-first

[boadij]

Closes #208

Summary

• Make Manager-assigned project Leads orchestration-first for substantial bounded execution, not implementation alone.
• Remove independence/context-heaviness as the generic delegation eligibility gate while keeping trivial, inseparable, unsuitable, or coordination-negative work local.
• Clarify Lead ownership of architecture, scope, integration, acceptance of Agent outputs, conflict resolution, and technical decisions; Manager retains project resolution.
• Align DELEGATING_AGENT_SCOPE_DESCRIPTION with the generalized contract: it also imposed the contradictory “bounded independent or unfamiliar” eligibility gate, so its instructions and contract coverage now match the generic guideline.
• Keep Agent ownership and automatic settled-run handoff unchanged; update current runtime-contract projections and focused tests.

Architecture

No new runtime mechanism. The existing project assignment identifies the stronger project-Lead posture; existing Pi promptGuidelines remain the high-salience generic delegation surface. ADR 0003 and ADR 0012 remain unchanged.

Validation

• npm test -- extension/extension-contract.test.ts
• npm test -- extension/commands.test.ts
• npm run check
• git diff --check

[boadij]

Resolved External Review #1 in the rebased branch:\n\n- Rebased onto current .\n- Preserved #223 across all ten file-capable tools and its contract coverage; removed the obsolete one-tool assertion.\n- Removed misleading “As a Lead” wording.\n- Added direct-execution exception coverage for trivial, inseparable, or otherwise unsuitable work.\n- Removed review execution from retained Lead responsibilities because review can be delegated.\n\nValidation: 42 and 75 focused tests passed;