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- mode-watcher (0 imports; superseded by stores/theme.svelte.ts)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/activity.ts

@@ -161,7 +161,7 @@ export const activityLog = derived([messages, planSteps, currentTask], ([$msgs,
   // which caused the AgentIndicator to latch onto a stale "Approval: ..."
   // entry and never clear — even after the session completed. Approvals
   // are tracked via the REST /approvals endpoint (context.ts, Ops.svelte)
-  // and rendered as InlineApproval cards in the chat (or Ops page), not
+  // and rendered as inline approval cards in the chat (or Ops page), not
   // in the activity log.
 
   // Sort oldest first