Close Γ-W1-T7 re-review: pitch-sync cadence math, floor-model regression check, evidence-count fix, one-home comments

New cadence-collapse-band test at P=1470 shows PSOLA eliminates the corner rather than regressing it (18.52% -> 0.00%).

src/core/instrument/CLAUDE.md

@@ -289,13 +289,13 @@ anything for a trigger shape.
 - `engine/loop/` — the sustain loop's ONE validity/clamp fold (`resolveLoop`) plus its pre-seam crossfade geometry and the editor's default handle span; see `engine/loop/CLAUDE.md`. The voice folds it once at note-on; the crossfade weight is header-inline because it rides the per-sample read.
 - `pitch_shift` — hand-rolled **correlation-aligned SOLA** (splice-overlap-add) pitch shifter AND time-stretcher for the Preserve playback mode: one active read tap chases the write head at the shift ratio; each splice jump is refined by a cross-correlation search so the new read point is waveform-aligned, then old and new taps are crossfaded (raised-cosine, amplitude-complementary). Replaces the prior dual-tap OLA whose fixed half-window tap offset caused anti-phase cancellation on many source frequencies. **GA2:** ring buffer **primed with the actual upcoming source** at note-on (was zero-filled) → gap-free frame-0 onset, ~25 ms Preserve onset latency eliminated (Preserve now speaks on frame 0, matching Varispeed), and real-content-bounded tail (last-window tail-truncation gone). No third-party dependencies; RT-discipline: no allocation in `process()`.
   - **The WRITE rate (duration) and the TAP rate (pitch) are independent, and that is the whole time-stretcher** — `writeFrame` for a surplus source frame, `processNoInput` for a starved output frame, plain `process` for the 1:1 case, `setShiftRatio` for pitch, and `setFeedRate` so the splice crossfade is sized against the real drain rate. The header owns the argument, including why this is not the resampled-read-with-a-cancelling-shift the `WDL_Resampler` invariant above forbids.
-  - **Splices are PITCH-SYNCHRONOUS when the source's period is known** (`setSourcePeriod`, fed from `period_detect` via the loader): the nominal jump becomes the multiple of that period nearest the window that still fits the ring's jump bound (~1.25 windows), so an aligned landing point sits at the CENTRE of the correlation search instead of possibly not existing inside it at all. The search is unchanged and still earns its keep — it absorbs the jump's rounding to whole frames and tracks a source whose period drifts. **An unknown period restores the fixed-window geometry byte for byte**; do not "simplify" that fallback into an approximation of it.
+  - **Splices are PITCH-SYNCHRONOUS when the source's period is known** (`setSourcePeriod`, fed from `period_detect` via the loader): the nominal jump becomes the multiple of that period nearest the window that still fits the ring's jump bound (~1.25 windows), so an aligned landing point sits at the CENTRE of the correlation search instead of possibly not existing inside it at all. The search is unchanged and still earns its keep — it absorbs the jump's rounding to whole frames and tracks a source whose period drifts. **An unknown period restores the fixed-window geometry exactly** (`periodAlignedJump`, `pitch_shift.h`); do not "simplify" that fallback into an approximation of it.
 - `period_detect` — the source's own fundamental period, estimated ONCE per load (two-pass YIN:
   a decimated cumulative-mean-normalized difference picks the period, the full-rate difference
   function refines it to a fraction of a frame), so `pitch_shift`'s splice jump can be a whole
-  number of it. **It runs off the audio thread BY LINK GRAPH: `sampler_core` does not link it**,
-  so no TU on the render path can name `detectPeriod` — the same shape as the extension's link
-  graph not gaining the voice engine. Its one caller is the loader (`map/sample_map`'s
+  number of it. **Runs off the audio thread by link graph** (`period_detect.h` is the one home
+  for that invariant) — the same shape as the extension's link graph not gaining the voice
+  engine. Its one caller is the loader (`map/sample_map`'s
   `buildSampleData`), which hands the answer down on `SampleData::sourcePeriodFrames`. A period
   is DERIVED from the audio, so it is cache and not state: nothing persists it, and it takes no
   rung of the payload ladder. **Answering "none" is a first-class result** — noise, polyphony,