feat(gig-log): k:'rec' — two lenses on Ardour actually recording

'Recording X had track Y playing at time Z' becomes answerable. Files lens =
ground truth (stems growing in interchange/, stat-only, 2s grace, RecPass state
machine); OSC lens = Ardour's own word (/set_surface feedback=8 handshake to
:3819, listens :3820, /rec_enable_toggle + transport — the manual's real name
for master arm, not /rec_enabled). Records on transitions + every tick while
recording; lens disagreement ships as conflict:true, never smoothed over.
44 new tests (155 total green), stdlib-only, --no-rec escape hatch.