feat(planning): robust plan JSON repair + schema validation with env toggle

[AntonioVFranco]

Summary

Robust JSON repair and schema validation for LLM-produced plans, plus integration into PlanningFlow with a safe fallback.

Changes

• Add app/planning/:
  • models.py (Plan, Step, extra='forbid')
  • json_repair.py (fences, smart quotes, JS comments, trailing commas incl. whitespace, in-string newline/tab escaping, single-missing brace/ bracket balance, 30% sanity guard)
  • collector.py (extract → repair → json.loads → Plan.model_validate)
  • metrics.py (lightweight counters)
  • integrations.py (parse_plan_text() adapter with env toggle)
• Wire parse_plan_text() into app/flow/planning.py with a strict json.loads + Plan.model_validate fallback.
• Log planning repair metrics in PlanningFlow.
• Docs: docs/planning-json-repair.md.

Toggle

• Default: enabled (repair + validate).
• Disable (strict mode): OPENMANUS_PLANNING_REPAIR=0.

Backwards compatibility / rollback

• Fully backwards compatible: fallback path keeps legacy behavior.
• Rollback: set OPENMANUS_PLANNING_REPAIR=0 to force strict mode.

Testing

• Local: export PYTHONPATH=$PWD && pytest -q tests/planning (9 passing).
• Pre-commit hooks are green.

Notes

• Title and commits follow Conventional Commits.

[AntonioVFranco]

Hi! This PR adds robust plan JSON repair & schema validation and wires it into PlanningFlow (with a strict fallback). Could you please review? Maintainers’ edits are allowed.

cc @mannaandpoem @XiangJinyu @MoshiQAQ @didiforgithub @stellaHSR @fred913

[AntonioVFranco]

On the Checks tab I'm seeing "Workflow runs completed with no jobs". Could a maintainer enable/run workflows for this PR or confirm that path filters make this expected?

Local verification: pytest -q tests/planning (9 passing) and pre-commit hooks are green. Thanks!