refactor(web): delete dead code (R2) — 1736 lines removed

Tool-renderer registry (21 files, ~1.5k lines):
- src/lib/tool-renderers.ts — registry + getToolRenderer (exported, never
  imported anywhere)
- src/lib/renderers/index.ts + 10 .ts registrars + 10 .svelte components
- main.ts: removed the requestAnimationFrame(() => import('./lib/renderers'))
  that was the only thing keeping the dead subsystem alive

Dead components (never imported):
- ToolCallGroup, PlanProgress, GoalHeader, InlineApproval, SessionDigest

Dead store exports (written, never read):
- context.ts: pendingApprovals writable (+ Approval type import)
- events.ts: connectionState writable (+ its .set() calls)

Dead API surface:
- api.ts: SessionDigest interface + fetchSessionDigest (only caller was the
  dead SessionDigest.svelte)

Dead npm deps:
- mode-watcher (0 imports; superseded by stores/theme.svelte.ts)
- @internationalized/date (0 imports)

Also: fix stale comments referencing deleted symbols, update plan R1/R2
status. Build clean (4683 modules, down from 4706; one Svelte 5 warning
gone — the dead HealthSummary.svelte was emitting state_referenced_locally).

web/src/lib/stores/events.ts

@@ -15,20 +15,16 @@ export interface OikosEvent {
 const MAX_BUFFERED = 200
 
 export const liveEvents = writable<OikosEvent[]>([])
-export const connectionState = writable<'connecting' | 'open' | 'closed'>('connecting')
 
 let source: EventSource | null = null
 let subscriberCount = 0
 
 async function connect() {
   if (source) return
-  connectionState.set('connecting')
   // The browser's EventSource sends Last-event-ID automatically on reconnect.
   // sseUrl is async so the OIDC access token is refreshed if expired.
   source = new EventSource(await sseUrl('/api/v1/events/stream'))
 
-  source.onopen = () => connectionState.set('open')
-
   source.onmessage = (ev) => {
     try {
       const parsed: OikosEvent = JSON.parse(ev.data)
@@ -39,7 +35,7 @@ async function connect() {
   }
 
   source.onerror = () => {
-    connectionState.set('closed')
+    // browser will auto-reconnect; nothing to surface here
   }
 }