feat: prototype Omnigent SDLC role-agent definitions

[smota]

Epic: #27

Summary

Prototype or document Omnigent custom agent definitions for SDLC roles while keeping single-agent execution as the baseline.

Acceptance criteria

• Example role-agent definitions or documented stubs exist for product manager/JTBD, analyst, architect, developer, reviewer, tech writer, and PR readiness.
• Examples reference existing SDLC docs and role-pass contracts.
• Docs explain these are optional Omnigent examples, not required workflow behavior.
• Any executable examples avoid secrets and local-only assumptions.

Test plan

• Validate YAML/examples if added.
• Run pnpm format:check.
• Run pnpm test:workflow if templates change.

Workflow classification

• Type: feature / dx / documentation
• 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.