feat: buffered canvas playback

[daibhin]

Problem

Canvas playback tried to preload every canvas as an image at the start of a recording. Browser memory said no.

Reported in https://posthoghelp.zendesk.com/agent/tickets/15204

Changes

• Adds a buffer that stores up to 30s or 20 canvas snapshots in memory
• Prunes every time a new canvas element is met
• Resets the buffer when scrubbing

How did you test this code?

Locally to ensure that recordings still worked. Canvas plays back so much better 👨‍🍳

[github-actions[bot]]

Size Change: 0 B

Total Size: 1.06 MB

ℹ️ View Unchanged

Filename	Size
frontend/dist/toolbar.js	1.06 MB

_{compressed-size-action}

[posthog-bot]

📸 UI snapshots have been updated

1 snapshot changes in total. 0 added, 1 modified, 0 deleted:

• chromium: 0 added, 1 modified, 0 deleted (diff for shard 2)
• webkit: 0 added, 0 modified, 0 deleted

Triggered by this commit.

👉 Review this PR's diff of snapshots.

[posthog-bot]

This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, post a comment or remove the stale label – otherwise this will be closed in another week.