Phase whygraph scan into three ordered phases with a results panel

[cvetty]

What & why

whygraph scan already sequenced git/GitHub before the LLM analyzer, but every crawler's progress bar was registered at construction and all five were built before any thread started — so the run looked fully parallel even though it wasn't. This makes the real structure visible and sharpens it.

Changes

• Three ordered phases: Phase 1 git + github (concurrent) → Phase 2 pr-origins → Phase 3 analyze (the slow, token-heavy LLM long pole, run last and alone). codegraph stays a best-effort background task started before Phase 1 and joined after Phase 3.
• Per-phase bar reveal: each phase's crawlers are constructed when its phase starts, so bars appear per-phase instead of all at once — no change to the Crawler render path.
• Presentation: icon'd, numbered console.rule headers (numbered against the count of phases that actually run), per-phase timing + a dim ✓ … (Ns) completion line, and a Progress column set with MofNCompleteColumn + TimeElapsedColumn so the LLM phase reports 12/45 · 0:00:31.
• Closing results panel bookending the pre-scan preview: per-phase status glyph (✓/⚠/✗/— skipped), summary, timing, and total elapsed — fed by a single additive Crawler.summary attribute set by each crawler's work().
• --no-llm-descriptions help text updated (no hard-coded phase number).

Behavior-preserving

Sequencing analyze last does not change what gets described: its todo is bounded by repository.commits (the main walk), which never includes on_default_branch=0 origin rows — so recovered PR-origin commits stay on lazy backfill exactly as before. Pinned by a new test.

Testing

• New tests/test_cli_scan_phases.py: phase-ordering (LLM strictly last), numbered-header counts (1/3, 1/2, 1/1), skip cases, and a defensive/total results-panel unit test.
• Extended test_git_crawler.py / test_scan_analyze_crawler.py: Crawler.summary strings + the origin-commits-stay-lazy behavior pin.
• 527 passed; ruff check and ruff format --check clean.
• Manually smoke-tested the rendered output (headers, per-phase bars, results panel) in a throwaway repo.

Notes

• Bars now share the stderr console (consistent with the pre-scan panel); non-TTY paths (hooks/CI/Docker) auto-degrade rich to plain lines, so automation is unaffected.
• Icon set (🔎/🔗/🧠/🕸) lives in one dict for easy swapping.