The TUI comparison picker silently ignored --model-a/--model-b (only the
--format json path used them), and both paths required the canonical model
id verbatim with no way to pass the display name the picker itself shows
(e.g. "Opus 4.8" for claude-opus-4-8).
Adds findModelStat, a shared lookup that matches the canonical id first and
falls back to getShortModelName's existing canonical -> display mapping
(case-insensitive) rather than a new alias table. Both the JSON path and
renderCompare/CompareView now use it; renderCompare resolves --model-a/
--model-b up front and seeds CompareView's picked-models state so results
load immediately instead of showing the picker. Also validates "both or
neither" for the TUI (default) format, matching the JSON path.
Fixesgetagentseal/codeburn#767 (item 1).
The #782 titles threading added title to the sessions JSON row shape but
missed this emitter test's key list; caught by the first full-suite run
since the merge.
Co-authored-by: reviewer <review@local>