feat(conflicts): add file overlap conflict detection (S-1 Phase 1)

Detects when 2+ agent sessions write the same file within a project.
New conflicts.svelte.ts store, shared tool-files.ts utility, dispatcher
integration, health attention scoring (SCORE_FILE_CONFLICT=70), and UI
indicators in ProjectHeader + StatusBar. 170/170 tests pass.

v2/src/lib/components/StatusBar/StatusBar.svelte

@@ -2,6 +2,7 @@
   import { getAgentSessions } from '../../stores/agents.svelte';
   import { getActiveGroup, getEnabledProjects, setActiveProject } from '../../stores/workspace.svelte';
   import { getHealthAggregates, getAttentionQueue, type ProjectHealth } from '../../stores/health.svelte';
+  import { getTotalConflictCount } from '../../stores/conflicts.svelte';
 
   let agentSessions = $derived(getAgentSessions());
   let activeGroup = $derived(getActiveGroup());
@@ -15,6 +16,7 @@
   let health = $derived(getHealthAggregates());
   let attentionQueue = $derived(getAttentionQueue(5));
 
+  let totalConflicts = $derived(getTotalConflictCount());
   let showAttention = $state(false);
 
   function projectName(projectId: string): string {
@@ -67,6 +69,12 @@
       </span>
       <span class="sep"></span>
     {/if}
+    {#if totalConflicts > 0}
+      <span class="item state-conflict" title="{totalConflicts} file conflict{totalConflicts > 1 ? 's' : ''} — multiple agents writing same file">
+        ⚠ {totalConflicts} conflict{totalConflicts > 1 ? 's' : ''}
+      </span>
+      <span class="sep"></span>
+    {/if}
 
     <!-- Attention queue toggle -->
     {#if attentionQueue.length > 0}
@@ -173,6 +181,11 @@
     font-weight: 600;
   }
 
+  .state-conflict {
+    color: var(--ctp-red);
+    font-weight: 600;
+  }
+
   .pulse {
     width: 6px;
     height: 6px;

v2/src/lib/components/Workspace/ContextTab.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
   import { getAgentSession, getTotalCost, type AgentSession } from '../../stores/agents.svelte';
   import type { AgentMessage, ToolCallContent, CostContent, CompactionContent } from '../../adapters/sdk-messages';
+  import { extractFilePaths } from '../../utils/tool-files';
 
   interface Props {
     sessionId: string | null;
@@ -195,41 +196,6 @@
     return Math.ceil(text.length / 4);
   }
 
-  function extractFilePaths(tc: ToolCallContent): { path: string; op: string }[] {
-    const results: { path: string; op: string }[] = [];
-    const input = tc.input as Record<string, unknown>;
-
-    switch (tc.name) {
-      case 'Read':
-      case 'read':
-        if (input?.file_path) results.push({ path: String(input.file_path), op: 'read' });
-        break;
-      case 'Write':
-      case 'write':
-        if (input?.file_path) results.push({ path: String(input.file_path), op: 'write' });
-        break;
-      case 'Edit':
-      case 'edit':
-        if (input?.file_path) results.push({ path: String(input.file_path), op: 'write' });
-        break;
-      case 'Glob':
-      case 'glob':
-        if (input?.pattern) results.push({ path: String(input.pattern), op: 'glob' });
-        break;
-      case 'Grep':
-      case 'grep':
-        if (input?.path) results.push({ path: String(input.path), op: 'grep' });
-        break;
-      case 'Bash':
-      case 'bash':
-        // Try to extract file paths from bash commands
-        const cmd = String(input?.command ?? '');
-        const fileMatch = cmd.match(/(?:cat|head|tail|less|vim|nano|code)\s+["']?([^\s"'|;&]+)/);
-        if (fileMatch) results.push({ path: fileMatch[1], op: 'bash' });
-        break;
-    }
-    return results;
-  }
 
   function formatTokens(n: number): string {
     if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(1)}M`;

v2/src/lib/components/Workspace/ProjectHeader.svelte

@@ -80,6 +80,12 @@
     <span class="project-id">({project.identifier})</span>
   </div>
   <div class="header-info">
+    {#if health && health.fileConflictCount > 0}
+      <span class="info-conflict" title="{health.fileConflictCount} file conflict{health.fileConflictCount > 1 ? 's' : ''} — multiple agents writing same file">
+        ⚠ {health.fileConflictCount} conflict{health.fileConflictCount > 1 ? 's' : ''}
+      </span>
+      <span class="info-sep">·</span>
+    {/if}
     {#if contextPct !== null && contextPct > 0}
       <span class="info-ctx" style="color: {ctxColor()}" title="Context window usage">ctx {contextPct}%</span>
       <span class="info-sep">·</span>
@@ -224,6 +230,16 @@
     flex-shrink: 0;
   }
 
+  .info-conflict {
+    font-size: 0.6rem;
+    color: var(--ctp-red);
+    font-weight: 600;
+    white-space: nowrap;
+    background: color-mix(in srgb, var(--ctp-red) 12%, transparent);
+    padding: 0.0625rem 0.375rem;
+    border-radius: 0.1875rem;
+  }
+
   .info-profile {
     font-size: 0.65rem;
     color: var(--ctp-blue);