feat: record Omnigent session evidence in workflow artifacts

[smota]

Epic: #27

Summary

Add optional Omnigent session metadata guidance to role-pass, handover, workflow-status, and PR-readiness evidence.

Acceptance criteria

• Templates or docs include optional Omnigent session URL/id fields.
• Evidence guidance captures selected harness, sandbox provider, policy profile, and actual executor where applicable.
• Docs warn not to expose secrets, private prompts, or sensitive session content.
• Non-Omnigent projects remain unaffected.

Test plan

• Run pnpm test:workflow.
• Run pnpm format:check.
• Validate PR manifest examples.

Workflow classification

• Type: feature / documentation / dx
• Suggested profile: standard
• Default execution: single-agent

[smota]

Corrected issue labels after provenance review:

• replaced incorrect drafted-by:claude with drafted-by:pi because these issues were created by the current Pi runtime;
• removed over-applied documentation where documentation is a supporting deliverable rather than the primary work;
• left documentation on chore: document Omnigent-powered SDLC scenarios #31 because that child issue is documentation-first.

Follow-up structural fix opened as #34.

[github-actions]

Integrated into development by PR #35: https://github.com/smota/multi-agent-sdlc/pull/35

Merge commit: 2866f00a11e2d38d291c0b440cdd521ec8c78f81
Release/promotion to main is tracked separately.