[lll-hhh]

Fixes #589.

In changes-description mode, routing required an exact SEARCH match even though patch application accepts differences in trailing whitespace. Valid code edits could be omitted, or the worker could discard a valid description update as unchanged.

Reuse the existing exact-then-trailing-whitespace matcher for routing. Keep leading indentation significant, and reject ambiguity whenever the same SEARCH block can apply to both code and the description under those matching rules.

Tests cover both directions of trailing-whitespace differences, ambiguity, significant indentation, and complete worker application/rejection paths with mocked LLM and evaluator boundaries.

Validation:

• The new regression suite produced five failure reports on the unmodified base (including subtests).
• On Ubuntu / Python 3.12.16, with the package installed: OPENAI_API_KEY=test-key-for-unit-tests python -m unittest discover tests — all 1,074 tests passed in 196.454s.
• Both repository pre-commit hooks (isort and Black) and git diff --check passed.
• The Windows full-suite attempt had environment-specific failures; the passing full-suite result is the Linux run. No live model requests were used for this fix.

Assisted by OpenAI Codex for investigation, implementation, and local validation.