capture: close batch-quarantine silence, 0-byte asymmetry, and round-two doc overclaims

Batch captures now name the retained-render folder once instead of nothing; Auto/Manual tail modes refuse a 0-byte render like None does; VERIFICATION.md steps 1-3 no longer invite a false conclusion; docs/comments no longer overclaim.

docs/VERIFICATION.md

@@ -27,9 +27,9 @@ Checks for Θ, Ξ, and Ψ work that no unit test can close. Build **Release**, i
 - [ ] 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`)
 - [ ] **Open blocker — root cause unknown; the three steps below are the experiment** (both live hypotheses and what is NOT yet excluded: `docs/TODO.md` §An offline capture can be refused for a short render). A live capture over [0.000000s, 4.067797s) was refused 38 frames short (195216 of 195254 at 48 kHz). Set View → time unit to Samples first
-- [ ] **Step 1 — does the item-scope render bound itself to the media?** This only tests anything if item scope actually reaches REAPER's selected-items render, and it does that ONLY when the selected items' extent already equals the requested window (`itemExtentPrintsWindow`, `src/core/capture/render_window.h`); otherwise item scope re-sources through the items' own tracks — the same source track scope uses, so the two runs would test one thing twice. So: snap the time selection to the item's exact start and end, run **item** scope, then **track** scope over the identical range. Report both `Render source:` lines and both frame counts. **If both lines read `selected tracks via master`, the item path was NOT exercised** — the extents did not match; re-snap and repeat before concluding anything
-- [ ] **Step 2 — full-length or short?** Extend the same range ~1 s past the end of all media, **track** scope. Landing with the full range (no refusal, the card reads the extended length) rules out BOTH a trailing-silence trim and a content-extent bound at once. A short render does NOT tell them apart: a trim firing despite `RENDER_NORMALIZE &(4<<16)` and a render bounding itself to content extent produce the same count. Report which happened, then run step 3
-- [ ] **Step 3 — where are the missing frames?** A refused render is kept deliberately, not deleted: it is moved to `<project folder>/reasampler_refused/`. **Follow the path in the refusal line, not this sentence** — if the move itself failed the file stays in the bank folder, unindexed, and the line says which happened. Insert it against the source over the same range and report whether the head aligns. Frames missing from the TAIL with an aligned head fits either a tail trim or a content-extent bound; a head offset fits neither and is a start-position defect. Also report whether the media under the range ends before the range does. Delete `reasampler_refused/` when done — nothing in the bank references it
+- [ ] **Step 1 — does the shortfall follow the render source?** This only tests anything if item scope actually reaches REAPER's selected-items render, and it does that ONLY when the selected items' extent already equals the requested window (`itemExtentPrintsWindow`, `src/core/capture/render_window.h`); otherwise item scope re-sources through the items' own tracks — the same source track scope uses, so the two runs would test one thing twice. So: snap the time selection to the item's exact start and end, run **item** scope, then **track** scope over the identical range. Report both `Render source:` lines and both frame counts. **If both lines read `selected tracks via master`, the item path was NOT exercised** — the extents did not match; re-snap and repeat before concluding anything. **A landing `&32` run here is not evidence `&32` honours custom bounds** — at a window snapped to the item's own extent, a render that honours the window and one that bounds itself to media content print IDENTICAL frames, so this step cannot tell those two apart; it only tells you which render source is in play. **If neither run refuses at this snapped range, the blocker did not reproduce here** — this range does not recreate the original refusal, which ran past the end of its media; move to step 2, which does
+- [ ] **Step 2 — full-length or short?** Extend the same range ~1 s past the end of all media, **track** scope. Landing with the full range (no refusal, the card reads the extended length) rules out BOTH a trailing-silence trim and a content-extent bound at once — but it also means there is no refused render for step 3 to read; re-run the ORIGINAL refusing range ([0.000000s, 4.067797s), track scope) to produce one before continuing. A short render does NOT tell the two hypotheses apart: a trim firing despite `RENDER_NORMALIZE &(4<<16)` and a render bounding itself to content extent produce the same count — and that render IS the one step 3 reads. Report which happened, then run step 3
+- [ ] **Step 3 — where are the missing frames?** Reads the short render from step 2 (or, if step 2 landed, the fresh refused render from re-running the original range per step 2's note) — not anything step 1 may have left behind, since a correctly-snapped step 1 should not have refused at all. A refused render is kept deliberately, not deleted: it is moved to `<project folder>/reasampler_refused/`. **Follow the path in the refusal line, not this sentence** — if the move itself failed the file stays in the bank folder, unindexed, and the line says which happened. Filenames carry a timestamp/counter but no scope marker, so if more than one file has landed in `reasampler_refused/` by now, the one from step 2 is the most recently written one — or empty the folder before running step 2 so there is only one candidate. Insert it against the source over the same range and report whether the head aligns. Frames missing from the TAIL with an aligned head fits either a tail trim or a content-extent bound; a head offset fits neither and is a start-position defect. Also report whether the media under the range ends before the range does. Delete `reasampler_refused/` when done — nothing in the bank references it
 
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