refactor(causa): hoist perf-tier ladder to theme/, wire event-detail tier dot (rf2-6ja23)

[mike-thompson-day8]

Summary

Per the rf2-6ja23 audit (causa ux — performance-tier colour-tag audit across panels):

• Hoist the perf-tier ladder from panels/performance_helpers.cljc into a new day8.re-frame2-causa.theme.perf-tier ns. The ladder (classify-tier / tier-colour / tier-glyph / tier-label / over-budget? / default-budget-ms / tier-order) is design-system grade — one source of truth, spec-anchored, JVM-portable — not panel-local.
• performance_helpers.cljc re-exports from the new ns so existing call-sites resolve unchanged. Zero behaviour change in the Performance panel.
• Wire the first cross-panel consumer: event_detail handler-row renders a perf-tier coloured dot + label when :tags :duration-ms is present. Gated on (number? duration-ms) so malformed tags never produce a misleading green dot. The raw :duration-ms stays in the EDN dump for power users.
• Audit ledger in the new ns's docstring names every panel surface that should carry the tier-dot, its status (LIVE / blocked on trace-stream / follow-on bead), and the structural prereq (per-event :duration-ms per Spec 009 L38) blocking the rest. Future panel-wiring beads land against the same ladder.

Beads landed

• rf2-6ja23 — perf-tier audit; ladder hoisted to theme/, event-detail handler-row tier-dot wired, audit ledger documented.

Beads closed (already shipped)

• rf2-mqm2d — editor-protocol matrix extension for cursor/windsurf/zed shipped via spec(causa): extend editor-protocol matrix with :windsurf + :zed (rf2-mqm2d) #593; bead was still OPEN; closed.

Beads deferred (with bd notes)

• rf2-wm7z4 (Cmd-K command palette) — substantial new feature spanning every panel; warrants its own focused PR with palette infrastructure built first.
• rf2-1o9cq (v1.1 drop-in mode for non-re-frame2 apps) — already deferred to 2026-08-05; v1.1+ design-time decision.
• rf2-3gn4f (v1.1 opt-in localStorage conversation persistence) — already deferred to 2026-08-05; Lock 12 privacy-posture change requires Mike's call at v1.1 design time.
• rf2-0us27 (v1.1 per-cascade structured export) — already deferred to 2026-08-05; Lock 4 serialisation/round-trip design question requires Mike's call at v1.1 design time.

Test plan

• cd tools/causa && clojure -M:test — 497 tests / 1423 assertions (was 488 / 1363), 0 failures
• cd implementation && npm run test:cljs — 1837 tests, 0 failures
• +9 theme.perf-tier ladder tests (boundaries, fallbacks, shape ↔ colour alignment)
• +6 event-detail handler-row tier-dot tests (each tier + absent + non-numeric guards)
• Test walker gains recursive descent through fn-component vectors so deep testids inside [handler-row ...] / [domino-row ...] bodies are reachable