refactor(lineage): fold whole-model-impact into the CLL experience

[danyelf]

PR checklist

• Ensure you have added or ran the appropriate tests for your PR.
• DCO signed

What type of PR is this?

refactor

What this PR does / why we need it:

--whole-model-impact was a separate server flag whose only way to be enabled
also forced --new-cll-experience on. In practice whole-model impact is a
subset of the CLL experience — there's never a reason to have one without the
other. This PR removes the standalone flag and gates the whole-model-impact
surfaces on new_cll_experience instead, so the two always travel together:

• CLL on → new-CLL visuals and whole-model impact render
• CLL off → neither renders

Backend

• Drop the --whole-model-impact Click option, its flag dict entry, and the
  implied-flag block in recce/cli.py.
• Remove the two obsolete CLI tests.

Frontend (full merge — the wholeModelImpact identifier is gone, not aliased)

• RecceServerFlags no longer carries whole_model_impact.
• The lineage context drops its wholeModelImpact field (the computed
  wholeModelChangedNodeIds / wholeModelImpactedNodeIds data sets stay).
• computeImpactedSets always computes the whole-model sets — it's only ever
  called when newCllExperience && cll.
• The title chip + left stripe (NodeView), graph badge (LineageNode), and
  change-category text-label suppression now gate on newCllExperience — which
  every one of those sites already had in scope, so it's a direct substitution.

Which issue(s) this PR fixes:

Special notes for your reviewer:

• No behavior change for users already running --new-cll-experience: they now
  get the whole-model surfaces automatically (previously gated behind the extra
  flag).
• recce/data/ (embedded frontend bundle) is not included here — it's a
  generated artifact regenerated by the normal build/release step.
• Verified end-to-end against a DuckDB two-env project with
  --new-cll-experience: /api/flag returns new_cll_experience: true with no
  whole_model_impact key; the graph renders ADD/COLUMN badges, suppresses
  the category text labels, and NodeView shows the amber whole-model-impacted
  title chip + stripe on a downstream-impacted model.
• Checks: pnpm type:check / pnpm lint / pnpm run build clean; full frontend
  suite 3979 passed; pytest tests/test_cli.py 23 passed; black/isort/flake8
  clean.

Does this PR introduce a user-facing change?:

The whole-model impact highlighting (title chip, left stripe, column badges, and
suppression of change-category text labels) is now part of the new CLL experience
and enabled by `--new-cll-experience`. The separate `--whole-model-impact` flag
(and its `RECCE_WHOLE_MODEL_IMPACT` env var) has been removed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
recce/cli.py	68.89% <ø> (-0.09%)	⬇️
tests/test_cli.py	100.00% <ø> (ø)

... and 3 files with indirect coverage changes

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