docs: extract Open TODOs into TODO.md

Move CLAUDE.md "Open TODOs" content into a dedicated TODO.md so
CLAUDE.md keeps its role as orientation / build-commands /
architecture, and TODO.md becomes the single per-repo home for open
work and DONE history.

TODO.md splits open work into:
- jllama-specific: upstream feature exposure (skip_download is
  DONE, --spec-draft-backend-sampling / reasoning control /
  max_outputs / MtP / suppress_tokens are queued by policy), the
  similar-projects feature backlog, the GraalVM Native Image
  evaluation
- cross-cutting slice: jqwik pin, @VisibleForTesting audit,
  null-safety follow-up, SpotBugs effort=Max, additional ArchUnit
  rules
- Done history: the full strictness-ladder + workspace-migration
  trail (Werror, Checker, module-info @NullMarked, LogCaptor,
  setSkipDownload, LlamaSystemProperties cleanup, etc.)

CLAUDE.md "Open TODOs" section now carries only a pointer to
TODO.md and to workspace/crossrepostatus.md.

Cross-repo coordination: each of the 4 sibling repos does the same
extraction in this session.

https://claude.ai/code/session_01LzoKmqzgtQsELS5tsH4Wog

Author: claude