Settle the render window on the time selection and delete the experiment that proved it

The millisecond floor lives in the custom-bounds field, not the engine, so
RENDER_BOUNDSFLAG=2 is now the only bounds mode: the two-position type, the
console verdict and the STARTPOS/ENDPOS drift probe all go. capture.cpp 697 -> 622.

docs/VERIFICATION.md

@@ -26,11 +26,11 @@ Checks for Θ, Ξ, and Ψ work that no unit test can close. Build **Release**, i
 - [ ] Same source: track scope × time selection, and track scope × razor — same exact window (`PLAN.md:2136`)
 - [ ] One razor-union case (two disjoint areas, one track) — lands the requested window, no `ReaSampler capture failed:` line (`PLAN.md:2137`)
 - [ ] Capture an item whose extent already equals the window — still lands, unchanged (the byte-identity regression floor) (`docs/COMPLETED.md:829`)
-- [ ] **The millisecond floor — what to expect.** A custom-bounds render is known to floor its window's END to the millisecond and write the floored value back over `RENDER_ENDPOS`. Mechanism, why two `RENDER_BOUNDSFLAG` channels exist, and the two live observations behind this: `src/core/capture/render_settings.h`'s `RenderBoundsChannel` and `docs/TODO.md` "An offline capture can be refused...". **Both live observations started at `0s`, on the grid, so nothing is known about the START edge**
-- [ ] **The one experiment — does another bounds mode escape the floor?** This build renders on the TIME SELECTION channel (`RENDER_BOUNDSFLAG=2`, window handed over via `GetSet_LoopTimeRange`) instead of custom time bounds. On every return past the point a bounds channel is chosen (the format/mode/empty-range/no-project refusals answer earlier and print nothing), one line beginning `ReaSampler capture -- bounds channel:` prints — including the two paths that answer before any bounds are judged (unsupported format, no output file), which print `NOT JUDGED` rather than staying silent. Read the verdict: **the floor's signature is ONLY a sentence naming "floored to the millisecond"** — a bare SHORT with no such sentence means the shortfall's cause is unestablished, and LONG can never be the floor's signature (a floor only removes frames, never adds them). **(WITHIN TOLERANCE)** on a SHORT/LONG is the gate's ordinary ±1-frame edge-convention slack (`render_window.h`), not the floor — don't read it as either result, and it can mask a floor: a window whose start and end sit in the same millisecond bucket makes the floored count equal the exact one, so a real one-frame floor there reads as a bare SHORT (WITHIN TOLERANCE) with no floor sentence at all. **EXACT is the fix only when the line carries no further caveat.** The verdict checks the observed count against every millisecond-floored model of the window (start floored alone, end floored alone, both together) and names any that reproduce it — grid membership on either edge is a proxy for that collision, not the test itself, so the caveat can fire even when NEITHER edge sits on the millisecond grid (sub-millisecond remainders on the two edges can cancel under a full floor — a dragged, fixed-length time selection is the reproducible case). Re-run with a window the caveat doesn't name before trusting EXACT. **NOT JUDGED naming a bounds channel** means that capture answered nothing (tail mode was not None, the render was empty, the render never even reached a bounds check, or the window rounds to 0 frames at this rate) OR the render source itself is INFERRED (not SDK-confirmed) to derive its own bounds and never consult the channel — selected-items captures always read this way; razor edits never do today, because no offline capture path assigns `SourceMode::RazorArea` (razor is a range source resolved through track/item scope, not a render source of its own) — so pick a window narrower than the selected item(s) to route through the time-bounded source instead
-- [ ] **Same run, the START edge.** The verdict line also says whether the run tested the start. Capture a range whose start is NOT a whole millisecond (set View → time unit to Samples, then nudge the selection start off the grid) so the line reads `The START edge IS tested here`. Report that line verbatim — it is the only evidence available for whether the start floors too, and a start floor is the case that would break the null test silently rather than loudly
-- [ ] **Auto and Manual tail.** Repeat the off-grid-start/off-grid-end capture once with the panel tail toggle at **Auto** and once at **Manual**. Neither is judged against a frame count, so the evidence is the `after render` drift lines: report whether either channel's bounds read back changed. `[verify — DAW]` A tail is assumed to render PAST the window end — the SDK header (`:3048`) confirms only that `RENDER_TAILMS` is a length in ms, not that it extends past the end. If that assumption is wrong, an end floor could be costing Auto/Manual real content with no detector (`checkRenderedBounds` returns immediately for `tailMode != None`) — so also report by ear/measurement whether either tail capture comes up short against the source, not only whether the bounds fields drifted
-- [ ] Whichever way the experiment lands, the refused render is still kept for diagnosis at `<project folder>/reasampler_refused/` (the refusal line names the path; a failed move leaves it unindexed in the bank folder and says so). Delete the folder when done — nothing in the bank references it
+- [ ] **The millisecond floor — SETTLED, nothing to re-run for `TailMode::None`.** The floor lives in the custom-time-bounds field (`RENDER_BOUNDSFLAG=0`), not in the render engine. Two live 48 kHz `TailMode::None` renders on `RENDER_BOUNDSFLAG=2` (time selection, handed over via `GetSet_LoopTimeRange`) came back exact — 97627 frames against 97627 — the second over a window whose START carried a sub-millisecond remainder, with no floored model of that window able to reproduce the count. Time selection is now the only bounds mode a capture can reach; the console verdict line and the `RENDER_STARTPOS`/`ENDPOS` read-back probe that answered this are gone. Full observation: `src/core/capture/render_settings.h`'s `kRenderBoundsTimeSelection`
+- [ ] **Still open — Auto and Manual tail.** `checkRenderedBounds` judges `TailMode::None` only (Auto/Manual add frames by design), so the settled result covers those two by INFERENCE, not observation: the floor applied to the bounds identically on all three tail modes, and all three now hand the window over the same way. What would establish it: repeat an off-grid-start capture at **Manual** over a source that is loud right to the window's end, and check the landed file's frames against window + `tailMs` — a floored edge shows up in that count. **Auto** cannot be checked by count (it trims trailing silence), so it needs the null test by ear/inversion against the source instead
+- [ ] `[verify — DAW]` A tail is assumed to render PAST the window end — the SDK header (`:3048`) confirms only that `RENDER_TAILMS` is a length in ms, not that it extends past the end. If that assumption is wrong, a tail capture is silently SHORTER than its window with no detector at all. Report whether either tail capture comes up short against the source
+- [ ] A refused render is kept for diagnosis at `<project folder>/reasampler_refused/` (the refusal line names the path; a failed move leaves it unindexed in the bank folder and says so). Delete the folder when done — nothing in the bank references it
+- [ ] **If a capture is refused for a short render**, report the refusal line verbatim. A message naming `floored to the millisecond` means the floor is back on a mode measured escaping it; a shortfall of one or two frames with no such sentence may be the gate's own edge-convention tolerance rather than the render (`render_window.h`'s `renderHonoredBounds`)
 
 ## Names and channels