feat: begin Phase 5 explicit process definitions

[eshulman2]

Summary

• derive a strict process manifest from the same canonical workflow definition used for execution
• expose operation, gate and contract-backed station roles
• enumerate labelled transitions without inspecting LangGraph runtime state
• render deterministic Mermaid and JSON views
• compare workflow revisions and report added, removed and changed nodes
• identify missing resume mappings that can strand in-flight instances
• expose local forge workflow render and forge workflow diff commands
• keep station bindings in the compiler's allowlisted state-profile catalog

Stack

• Depends on refactor: begin Phase 4 station migration #327
• Implements Phase 5 inspection, visualization and structural change-impact slices
• Golden-path publication and mandatory-policy governance remain follow-up slices

Verification

• uv run ruff check src/ tests/unit/workflow/test_declarative_workflows.py
• uv run mypy src/forge/workflow/declarative/manifest.py
• uv run pytest tests/unit/ tests/workflow tests/contracts tests/flows -q --strict-markers — 2,836 passed