test(process): add contract-test suite for step-file workflows

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Description

Adds tests/process/ — a structural/contract test suite for the step-file workflows under _ai-memory/pov/workflows/ and the aim-model-dispatch sub-workflows.

These workflows are defined entirely in markdown (workflow.md + step files, no backing executable), so the suite validates their contracts rather than runtime behavior — the load-and-assert style used for DAG-integrity testing. No workflow or source files are modified; the change is purely additive test coverage.

Related Issue

Completes test coverage for the skill-script externalization series (merged in #163–#170) by adding process-level contract tests for the step-file workflows. No specific issue to auto-close.

Fixes #

Type of Change

• Test coverage (additive, no functional change)

Changes Made

• Add tests/process/ with contract tests parametrized across all 26 workflow.md files (both workflow roots) and 211 step files
• conftest.py: stdlib frontmatter parsing + step-chain walker, repo-root-anchored discovery (CWD-independent)
• Register a process pytest marker in pyproject.toml
• tests/process/INDEX.md: coverage map for all 30 processes

Testing

Test Environment

• Python Version: 3.10 / 3.11 / 3.12
• OS: Linux

Test Checklist

• Unit tests pass (pytest tests/)
• Manual testing completed

Test Cases Covered

1. Frontmatter schema — every workflow.md has name/description/firstStep; every step file has name/description
2. Step-chain integrity — firstStep and each nextStepFile resolve to a real file (no dangling references, cycle-guarded); terminal steps skip explicitly
3. Routing-map validity — every WORKFLOW-MAP.md routing entry resolves to a real workflow.md, with a cross-check so a malformed entry cannot silently drop from validation
4. Embedded-procedure skills — aim-agent-dispatch, aim-agent-lifecycle, aim-best-practices-researcher expose a valid SKILL.md
5. Corpus-size sentinel — fails loudly if the path anchors break, guarding against a silently-empty test run

Result: pytest tests/process/ -m process → 691 passed, 78 skipped. black / ruff / isort clean.

Documentation

• Code is self-documenting with clear names and docstrings
• tests/process/INDEX.md documents coverage — 28 processes tested; first-breath and model-dispatch/claude-native documented as non-feasible (open-ended dialogue / reference doc, no step chain)

Breaking Changes

• This PR introduces breaking changes

Security Considerations

• No sensitive data exposed — pure filesystem assertions, no src import, no live services required

Performance Impact

• No significant performance impact (filesystem-only tests, sub-minute runtime)

Deployment Notes

• No special deployment steps required

Checklist

• My code follows the project's coding conventions (PEP 8 for Python)
• I have performed a self-review of my code
• My changes generate no new warnings or errors
• I have added tests that prove the feature works
• New and existing unit tests pass locally with my changes
• I have updated the documentation accordingly