Roll Analysis: merge Batch and Roll into one searchable panel

[PabloRuizCuevas]

Summary

Merges Batch Analysis and Roll into one searchable panel — no more BATCH/ROLL subtitles to disambiguate two flows that both boiled down to "pick a baseline, apply it" — then carries Batch Analysis' own Lock Bounds handling to where it belongs.

• A searchable roll picker (SearchableGearCombo) replaces the plain "Select Roll…" combo and the separate magnifying-glass Batch Analysis button.
• Current Roll (the default entry) re-scans the loaded files; a saved name loads its stored baseline. One primary Apply button runs whichever is picked.
• Use Luma/Color Average moves below the picker+Apply row.
• Save/Delete stay; Delete disables on Current Roll, and Save rejects that name to avoid shadowing the picker's built-in entry.
• Lock Bounds now actually exempts a frame from Batch Analysis: a locked frame's stored floors/ceilings are left untouched on every re-run, instead of being silently re-enabled and overwritten.
• Batch Analysis reports which frames were trimmed out of the pooled interquartile-mean baseline on any channel. A trimmed frame still takes the roll average like everyone else — this is a report, not an exemption — but the status line now names it, since that frame's own measurement is, by construction, the furthest from the baseline about to land on it.

docs/USER_GUIDE.md (§4.3–4.4) and docs/PIPELINE.md are updated to match, along with the onboarding tutorial's Roll Analysis / Crosstalk steps.

Testing

• uv run ruff check .
• uv run ty check — no new diagnostics versus origin/main
• uv run pytest -q — full suite passes; only failure is the pre-existing tests/test_metadata_presets.py::TestPresetNames::test_load_tooltip_follows_a_rebinding
• tests/test_roll_sidebar.py, tests/test_batch_norm_wb.py, tests/test_controller.py, tests/test_section_help_dialog.py, tests/test_section_guides.py specifically cover the panel and the Lock Bounds/outlier fix

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