Honor M4 renderer cache invalidation

Preserve the renderer's `reset_cache` result when publishing
rebuilt paths so zoom changes invalidate Qt's cached graphics.
Retain the earlier live-debug provenance for cadence, negative
volume, repaint suppression, and downsample cache repair.

Prompt-IO: ai/prompt-io/opencode/20260903T232525Z_fadab3d2_prompt_io.md

(this commit msg was generated in some part by `codex` using
`gpt-6` (`openai`))

ai/prompt-io/opencode/20260903T232525Z_fadab3d2_prompt_io.md

@@ -0,0 +1,41 @@
+---
+model: gpt-5.6-sol
+service: opencode
+session: fsp-backfill-sync-live-volume
+timestamp: 2026-09-03T23:25:25Z
+git_ref: fadab3d2
+scope: code
+substantive: true
+raw_file: 20260903T232525Z_fadab3d2_prompt_io.raw.md
+---
+
+## Prompt
+
+Diagnose and fix MNQ's same-index volume repaint, missing post-closure
+volume curve, stale zoomed-out downsample path, and repeated
+`No yrange provided for dolla_vlm` warnings using live SHM evidence.
+
+## Response summary
+
+Declared source sample periods on `Flume` so FSP cascades cannot mistake
+a market-closure timestamp gap for their regular cadence. Clamped
+negative provider volume at sampling and volume-FSP boundaries, honored
+M4 renderer cache invalidation, and skipped unchanged realtime FSP
+redraws while retaining forced history repairs.
+
+## Files changed
+
+- `piker/data/flows.py` - declare RT/history sample periods.
+- `piker/data/_sampling.py` - prevent negative sampled volume.
+- `piker/fsp/_engine.py` - subscribe using the declared RT period.
+- `piker/fsp/_volume.py` - clamp volume history and trade sizes.
+- `piker/ui/_dataviz.py` - honor renderer cache resets.
+- `piker/ui/_fsp.py` - skip identical realtime FSP redraws.
+- `tests/test_fsp_sync.py` - cover the observed regressions.
+
+## Human edits
+
+The human identified each visual failure, supplied the exact console
+warning, confirmed that the later-started `flow_rates` cascade behaved
+correctly, requested declared cadence instead of timestamp inference,
+performed chart restarts, and live-validated the final behavior.

ai/prompt-io/opencode/20260903T232525Z_fadab3d2_prompt_io.raw.md

@@ -0,0 +1,71 @@
+---
+model: gpt-5.6-sol
+service: opencode
+timestamp: 2026-09-03T23:25:25Z
+git_ref: fadab3d2
+diff_cmd: git diff HEAD~4..HEAD
+---
+
+## Prompt
+
+The human reported that the MNQ volume subchart repeatedly rendered
+its last bar at one index around the equity-futures closure, then
+reported that the volume curve disappeared after reopening. During
+live testing, the human confirmed that `flow_rates`, which started
+later, advanced correctly while `dolla_vlm` remained pinned. The human
+then reported a stale downsampled curve on zoom-out and supplied the
+repeated console warning:
+
+`No yrange provided for dolla_vlm!?`
+
+The human requested a live diagnosis and fix, validated each restart,
+and confirmed the final chart behavior was fixed.
+
+## Response
+
+Read-only SHM snapshots showed that `dolla_vlm` remained at exclusive
+bound `172801` while the source advanced hundreds of rows. Its one
+current row kept receiving current quote values, explaining the
+same-index repaint. `flow_rates` remained aligned because it started
+after regular one-second timestamps resumed.
+
+The cascade had inferred its sampler period from the last two distinct
+timestamps. A market closure therefore looked like the source cadence.
+Explicit `Flume` RT/history periods now drive sampling and downsampling
+metadata instead.
+
+> `git diff HEAD~4..HEAD -- piker/data/flows.py`
+
+> `git diff HEAD~4..HEAD -- piker/fsp/_engine.py`
+
+Further SHM inspection found an IB source row with volume `-2319096`.
+`dolla_vlm` multiplied that value into a `-68277471626` outlier, causing
+`Viz.maxmin()` to reject the zoomed-out range. Sample ingestion and
+volume FSP history/realtime calculations now clamp negative volume.
+
+> `git diff HEAD~4..HEAD -- piker/data/_sampling.py`
+
+> `git diff HEAD~4..HEAD -- piker/fsp/_volume.py`
+
+The M4 renderer already returned a cache-reset signal after rebuilding
+a downsampled path, but `Viz.update_graphics()` overwrote that signal
+with `False`. The override was removed so Qt's device-coordinate cache
+is invalidated with the new path.
+
+> `git diff HEAD~4..HEAD -- piker/ui/_dataviz.py`
+
+Normal quote cycles also redrew unchanged FSP state. A per-`Viz`
+bounds/timestamp/value signature now suppresses only identical
+realtime refreshes; forced history redraws still bypass it.
+
+> `git diff HEAD~4..HEAD -- piker/ui/_fsp.py`
+
+Regression coverage models closure-gap cadence, negative provider
+volume, unchanged realtime redraws, and the broader FSP synchronization
+behavior.
+
+> `git diff HEAD~4..HEAD -- tests/test_fsp_sync.py`
+
+Live verification after restart showed source and `dolla_vlm` advancing
+at the same bound, zero negative destination rows, and correct zoomed-out
+rendering. The focused suite completed with 38 passing tests.

piker/ui/_dataviz.py

@@ -985,10 +985,10 @@ class Viz(Struct):
         # XXX: SUPER UGGGHHH... without this we get stale cache
         # graphics that "smear" across the view horizontally
         # when panning and the first datum is out of view..
-        reset_cache = False
         if (
             reset_cache
-            or should_redraw
+            or
+            should_redraw
         ):
             # assign output paths to graphicis obj but
             # after a coords-cache reset.