Feat/compact instruction

[zlb22]

Related Issue

Resolve #544

Description

• Fix [tool.uv.build-backend].module-name (root, kosong, kaos) to use strings so uv and hooks parse correctly.
• Let /compact accept an optional hint /compact <summary hint> and pass it through to the compaction pipeline.
• SimpleCompaction appends User instruction: <hint> after the default prompts.COMPACT; defaults unchanged when
  no hint is provided.
• Update slash help text and add a unit test covering custom instruction injection.

Testing

• uv run pytest tests/test_simple_compaction.py -q