fix: add codebase verification step to task_planning to prevent duplicate TODOs

[Kailigithub]

Summary

Fixes #560

The task planning SOP (memory/autonomous_operation_sop/task_planning.md) previously only checked reports and memory files in Step 3, missing actual codebase state. This caused already-implemented features to be planned as new "evaluate/integrate" TODOs, wasting autonomous action turns.

Changes

Added Step 3.5 (现状核实) between Step 3 (inventory) and Step 4 (TODO generation):

• Before generating TODOs, check if candidate features/modules already exist in the codebase
• For output-type TODOs ("evaluate X" / "integrate X"), search related files and verify the feature is not already implemented before writing it
• Already-implemented features can only produce "optimize/enhance/test" TODOs, not "evaluate/integrate" ones

Verification

• Markdown content verified manually — the new step integrates naturally into the existing numbered flow
• The change is additive only (3 lines inserted), no existing content modified
• Aligns with the existing SOP structure and naming conventions

Closes #560