feat: open useful USER_TYPE-gated features to all users (#644)

* feat: open useful USER_TYPE-gated features to all users

Remove 13 process.env.USER_TYPE === 'ant' gates that restricted useful
features to Anthropic employees. These features work without Anthropic
infrastructure and are now available to all open-build users.

Features opened:
- Agent nesting (sub-agents can spawn sub-agents)
- Effort 'max' persistence in settings
- Plan mode interview phase (controlled by feature flags)
- Sandbox disabled commands (via ~/.claude/feature-flags.json)
- All tips visible to all users (plan mode, feedback, shift-tab)

Simplified:
- Fullscreen defaults to off (use /config to enable)
- Explore agent always uses haiku model
- Plan mode tool uses conservative prompt for all users

Continues the USER_TYPE cleanup from #637 (dead code) and builds
on #639 (local feature flags).

* fix: address Copilot review comments — remove residual dead code

1. bridgeConfig.ts: ungate bridge override functions — return env vars
   directly instead of hardcoded undefined
2. bridgeMain.ts + initReplBridge.ts: ungate sessionIngressUrl — read
   CLAUDE_BRIDGE_SESSION_INGRESS_URL without USER_TYPE check
3. tools.ts: remove dead ConfigTool/TungstenTool imports, narrow
   eslint-disable scope, stub REPLTool/SuggestBackgroundPRTool to null
4. readOnlyValidation.ts: remove orphaned ANT_ONLY_COMMAND_ALLOWLIST
   and unused GH_READ_ONLY_COMMANDS import
5. insights.ts: remove entire remote collection plumbing (types,
   functions, options, display logic)
6. osc.ts: hardcode supportsTabStatus() to false (internal-only feature)
7. state.ts: simplify addSlowOperation/getSlowOperations to no-ops,
   remove dead constants

* fix: address Copilot review on PR #644

1. settings/types.ts: allow 'max' effort level for all users in Zod
   schema — was still gated behind USER_TYPE=ant, causing 'max' to be
   silently dropped on settings reload
2. shouldUseSandbox.ts: defensively normalize disabledCommands from
   feature flag config with Array.isArray() guards

* fix: address second round of Copilot review on PR #644

1. shouldUseSandbox.ts: validate top-level shape of disabledCommands
   before accessing properties (handles null/primitive from feature flag)
2. fullscreen.ts: update JSDoc to reflect removal of USER_TYPE default
3. osc.ts: update JSDoc — "Ant-only" → "Currently disabled"

src/bootstrap/state.ts

@@ -1562,29 +1562,8 @@ export function clearInvokedSkillsForAgent(agentId: string): void {
   }
 }
 
-// Slow operations tracking for dev bar
-const MAX_SLOW_OPERATIONS = 10
-const SLOW_OPERATION_TTL_MS = 10000
-
-export function addSlowOperation(operation: string, durationMs: number): void {
-  if (process.env.USER_TYPE !== 'ant') return
-  // Skip tracking for editor sessions (user editing a prompt file in $EDITOR)
-  // These are intentionally slow since the user is drafting text
-  if (operation.includes('exec') && operation.includes('claude-prompt-')) {
-    return
-  }
-  const now = Date.now()
-  // Remove stale operations
-  STATE.slowOperations = STATE.slowOperations.filter(
-    op => now - op.timestamp < SLOW_OPERATION_TTL_MS,
-  )
-  // Add new operation
-  STATE.slowOperations.push({ operation, durationMs, timestamp: now })
-  // Keep only the most recent operations
-  if (STATE.slowOperations.length > MAX_SLOW_OPERATIONS) {
-    STATE.slowOperations = STATE.slowOperations.slice(-MAX_SLOW_OPERATIONS)
-  }
-}
+// Slow operations tracking removed (was internal-only).
+// Functions kept as no-ops to avoid breaking callers.
 
 const EMPTY_SLOW_OPERATIONS: ReadonlyArray<{
   operation: string
@@ -1592,32 +1571,17 @@ const EMPTY_SLOW_OPERATIONS: ReadonlyArray<{
   timestamp: number
 }> = []
 
+export function addSlowOperation(
+  _operation: string,
+  _durationMs: number,
+): void {}
+
 export function getSlowOperations(): ReadonlyArray<{
   operation: string
   durationMs: number
   timestamp: number
 }> {
-  // Most common case: nothing tracked. Return a stable reference so the
-  // caller's setState() can bail via Object.is instead of re-rendering at 2fps.
-  if (STATE.slowOperations.length === 0) {
-    return EMPTY_SLOW_OPERATIONS
-  }
-  const now = Date.now()
-  // Only allocate a new array when something actually expired; otherwise keep
-  // the reference stable across polls while ops are still fresh.
-  if (
-    STATE.slowOperations.some(op => now - op.timestamp >= SLOW_OPERATION_TTL_MS)
-  ) {
-    STATE.slowOperations = STATE.slowOperations.filter(
-      op => now - op.timestamp < SLOW_OPERATION_TTL_MS,
-    )
-    if (STATE.slowOperations.length === 0) {
-      return EMPTY_SLOW_OPERATIONS
-    }
-  }
-  // Safe to return directly: addSlowOperation() reassigns STATE.slowOperations
-  // before pushing, so the array held in React state is never mutated.
-  return STATE.slowOperations
+  return EMPTY_SLOW_OPERATIONS
 }
 
 export function getMainThreadAgentType(): string | undefined {