recording: pace drivers in content-time (lockstep follow-up)

[borisbat]

Follow-up to the lockstep-recording sweep (dasImgui #189 / #191, both merged). Converts the ImPlot recording drivers from wall-clock pacing to content-time, so beats match their intended length regardless of render rate and stay aligned with the voiceover.

Why

Under lockstep the recorder captures every rendered frame at a fixed 1/fps delay, so a wall-clock sleep(ms) yields render_rate/fps * ms of video (beats stretch on a fast machine and drift off the real-time voiceover). Content-time holds wait for ms/1000*fps captured frames, so a beat is exactly ms of video.

Changes (per driver)

• Drop the local wall-clock def hold_remainder(dwell, t0) helper; use dasImgui's hold_remainder_content.
• Anchor each beat in captured frames (record_frame_count) instead of ref_time_ticks.
• Convert pacing sleep(ms) → hold_content(app, ms) (leads, mid-beat dwells). Effect-waits (wait_for_mouse_idle / record_check_* / move_to) are untouched.
• Drop a pre-existing unused require implot (STYLE030) that lingered in three drivers — required for the now-changed files to pass the CI lint gate.

record_drag_tools.das needs no change: it already paces every beat with say() (content-time since #191) and has no wall-clock holds.

Validation

All 10 drivers lint clean (-load_module dasImgui -load_module dasImguiImplot). Re-recorded two self-verifying drivers end-to-end:

line_plot       869 frames / 30 fps = 28.967 s exactly,  dropped 0, exit 0
query_and_hover 802 frames / 30 fps = 26.733 s exactly,  dropped 0, exit 0

exit 0 means every record_check_* gesture assertion passed → the content-time holds stay in sync with the synth mouse/scroll timelines.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR updates the ImPlot integration recording drivers to pace narration beats in content-time (captured frames) rather than wall-clock time, so recorded beat lengths remain consistent regardless of render rate and stay aligned with voiceover.

Changes:

• Replaces wall-clock beat timing (ref_time_ticks() + sleep) with captured-frame timing (record_frame_count(app) + hold_content / hold_remainder_content).
• Removes per-file hold_remainder helpers in favor of the shared hold_remainder_content.
• Drops an unused require implot in the affected drivers to satisfy linting.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/integration/record_subplots.das	Switches beat lead/hold pacing to content-time; removes unused require implot and local hold_remainder.
tests/integration/record_shaded_and_stairs.das	Replaces wall-clock beat anchoring/holds with record_frame_count + hold_remainder_content.
tests/integration/record_realtime_scroll.das	Anchors the narration window to captured frames and uses hold_remainder_content; removes unused require implot.
tests/integration/record_query_and_hover.das	Converts beat timing to content-time and removes unused require implot.
tests/integration/record_multi_series.das	Uses hold_content for lead-in and hold_remainder_content for beat remainder timing.
tests/integration/record_multi_axes.das	Converts lead-in sleeps to hold_content and beat remainder to hold_remainder_content.
tests/integration/record_line_plot.das	Converts lead-in and intra-zoom pacing from sleep to hold_content, and uses hold_remainder_content for beat remainder.
tests/integration/record_heatmap_histogram.das	Switches beat anchors to captured frames and uses hold_remainder_content.
tests/integration/record_colormaps_and_style.das	Switches beat anchors to captured frames and uses hold_remainder_content.
tests/integration/record_bar_groups_and_pie.das	Converts lead-in and dwell sleeps to hold_content and uses hold_remainder_content for beat remainder.

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