v0.11.0 — package split, single-file curl build, 6× faster grep

• Package split: the single 2100-line module became the
  claude_handoff/ package — nine single-responsibility modules with
  acyclic imports (textutil, redact, parse, webexport,
  discovery, render, llm, integrations, cli). Proven
  mechanical: outputs byte-identical before/after on all fixtures and
  a real multi-agent session.
• curl still works: scripts/build_single.py stitches the package
  into the generated single/claude_handoff.py; CI fails if it goes
  stale or drifts behaviorally (--check).
• Performance: load_records streams (peak RSS on a 20 MB
  session: 80 MB → 26 MB); --grep prefilters with a raw-text
  superset scan in binary mode when JSON escaping cannot hide a
  match (worst-case store-wide search 3.3 s → 0.5 s).
• Lint: ruff config in pyproject.toml (E/F/I/PLW/RUF), codebase
  clean; new CI lint job.