feat(ui): search & filter — close out S3

[sepehr-safari]

Summary

Makes large traces navigable with search & filter, and closes out S3 —
Inspector UI (0.2.0).

• Free-text search — a real search_field (with its built-in clear
  affordance) matching action / unique id / payload substring, case-insensitive.
• Toggle facets — message type (Call / Result / Error), direction (from CP /
  from CSMS), and severity (participates in a failure of level X). Facets
  AND-compose with each other and the search.
• Instant + viewport-bounded — the filtered index set is derived in the build
  arena and becomes the virtual list's source, so a filtered huge trace never
  materializes hidden rows. The status bar shows N of M events; an empty result
  shows a quiet "no matching events".
• Clear — the search field's clear (x / Escape) arrives as a .clear edit
  through the same input path; a Clear button resets every facet and the query.

Design notes

• Filter lives on the Model, not per-trace. LoadedTrace values are memcpy'd
  during tab compaction, which would dangle a self-referential search slice. The
  Model has a stable address, and the query is stored as a fixed buffer + length
  • caret (no stored slice pointer), so the whole Filter stays trivially
    copyable. Edits apply into a scratch buffer then copy back — no aliasing.
• Controlled input via TextEditState. TextInputEvent is an edit delta, so
  update reconstructs the query with applyTextInputEvent. The headless tests
  drive the exact msgForTextEdit path the runtime uses.
• Derive once. view computes the filtered indices a single time and threads
  them to both the timeline and the status bar; unfiltered traces allocate no
  index array at all.

Testing

native test -Dplatform=null — 89 headless tests green (macOS local; CI runs
both OSes). New coverage:

• The free-text predicate (action / id / payload keys + values, case-insensitive,
  bounded), and the facet toggle + clear logic.
• Search build/delete/clear through real edit events; a message-type facet
  narrowing the count and the Clear button restoring it.
• A filtered 2000-event trace's whole widget tree stays under the node budget
  (no hidden-row materialization).
• The empty-result state, and the accessibility sweep over the active filter bar.

native check --strict clean; native build (ReleaseFast) builds. Living docs
(CURRENT_STATE.md, ROADMAP.md, AGENTS.md) updated in-branch and S3 marked
complete.

Deferred (tracked, not blockers)

Interactive open — native dialog + drag-drop (#33) — and the timeline viewport
scroll on jump both need an ejected runner (ADR-0006).

Closes #32