[lxsmnsyc]

Adds a Timeline tab that lists what each user action made the app do: the signals it wrote, every memo and effect that re-ran, why each one ran, and how long the update took. This PR is based on #28.

Changes

• The toolbar turns on the attribution engine from solid-js/attribution when it mounts, with log: false and values: 'full', so the first action is recorded even while the dock is closed.
• The panel reads the rerun, effect, flush, interaction, hold and navigation records from OBSERVE.records. Records of one interaction share its origin object, which is the key they are grouped by.
• Re-runs that no interaction caused, such as a timer or a promise, are grouped until the flush that ends them.
• Each row shows the writes, the number of re-runs and the total time. The detail shows the input delay, handler time and settle time, the writes with their old and new values, and each re-run.
• Opening a re-run shows its cause chain, such as report-doubled ← doubled changed ← write count 1 → 2. A run that produced the same value is marked as no change.
• The eye on a re-run opens the node in the reactivity graph.
• The copy button puts a Markdown report of the action on the clipboard. Values of writes with sensitive names are redacted.
• Interactions that wrote and ran nothing, such as clicks in the toolbar, are left out.
• Updates no action caused whose writes all went to unnamed signals, or that wrote nothing, are hidden by default. Most come from Solid's own state, such as a Show condition or a Loading boundary settling. A button above the list shows how many there are and brings them back, since an app's own unnamed signal looks the same.
• Durations under 0.1ms read as <0.1ms, since browsers round the clock.
• The panel keeps 100 actions and 300 re-runs per action.
• The panel also reads the call record. A call joins the action whose origin it carries, and lists with its method, status and time. Clicking it opens the call in the server-function panel.
• A click that only calls the server looks idle when its interaction record arrives. Idle interactions are kept aside, so a later call can attach to its own.

Example report

# Solid update: `click on button#increment-count "count 1 doubled 2"`

- Outcome: committed
- Input delay: 0.30ms
- Settled: 0.50ms after the event

## Writes

- write `count` 1 → 2

## Re-runs, in order

- memo `doubled` (<0.1ms)
  - ← write `count` 1 → 2
- effect `report-doubled` (<0.1ms, callback <0.1ms)
  - ← `doubled` changed
    - ← write `count` 1 → 2

Testing

• Unit tests in src/dev-toolbar/timeline/tracker.test.ts feed records by hand and cover grouping, outside updates, idle interactions, the entry limit, the snapshot copies and the report.
• A second e2e test clicks a button that only calls the server, checks the call under its action, and opens it in the server-function panel.
• A new e2e test clicks the counter, checks the row, the write, the three re-runs, the cause chain, and the jump to the graph.
• pnpm test, pnpm typecheck, pnpm format:check, pnpm build, pnpm check and the full e2e suite pass locally.

🤖 Generated with Claude Code