feat(v3): project-level tabs + clean AgentPane + ProjectHeader info bar

- ProjectBox: Claude|Files|Context tab bar switching content area
- ProjectFiles.svelte: project-scoped markdown file viewer
- ProjectHeader: CWD (ellipsized from start) + profile as info text
- AgentPane: removed DIR/ACC toolbar, CWD+profile now props from parent
- ClaudeSession: passes project.profile to AgentPane

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

@@ -0,0 +1,141 @@
+<script lang="ts">
+  import { discoverMarkdownFiles, type MdFileEntry } from '../../adapters/groups-bridge';
+  import MarkdownPane from '../Markdown/MarkdownPane.svelte';
+
+  interface Props {
+    cwd: string;
+    projectName: string;
+  }
+
+  let { cwd, projectName }: Props = $props();
+
+  let files = $state<MdFileEntry[]>([]);
+  let selectedPath = $state<string | null>(null);
+  let loading = $state(false);
+
+  $effect(() => {
+    loadFiles(cwd);
+  });
+
+  async function loadFiles(dir: string) {
+    loading = true;
+    try {
+      files = await discoverMarkdownFiles(dir);
+      const priority = files.find(f => f.priority);
+      selectedPath = priority?.path ?? files[0]?.path ?? null;
+    } catch (e) {
+      console.warn('Failed to discover markdown files:', e);
+      files = [];
+    } finally {
+      loading = false;
+    }
+  }
+</script>
+
+<div class="project-files">
+  <aside class="file-picker">
+    {#if loading}
+      <div class="state-msg">Scanning...</div>
+    {:else if files.length === 0}
+      <div class="state-msg">No files found</div>
+    {:else}
+      <ul class="file-list">
+        {#each files as file}
+          <li>
+            <button
+              class="file-btn"
+              class:active={selectedPath === file.path}
+              class:priority={file.priority}
+              onclick={() => (selectedPath = file.path)}
+            >
+              {file.name}
+            </button>
+          </li>
+        {/each}
+      </ul>
+    {/if}
+  </aside>
+
+  <main class="doc-content">
+    {#if selectedPath}
+      <MarkdownPane paneId="pf-{projectName}" filePath={selectedPath} />
+    {:else}
+      <div class="state-msg full">Select a file</div>
+    {/if}
+  </main>
+</div>
+
+<style>
+  .project-files {
+    display: flex;
+    height: 100%;
+    overflow: hidden;
+    flex: 1;
+  }
+
+  .file-picker {
+    width: 10rem;
+    flex-shrink: 0;
+    background: var(--ctp-mantle);
+    border-right: 1px solid var(--ctp-surface0);
+    overflow-y: auto;
+    padding: 0.25rem 0;
+  }
+
+  .file-list {
+    list-style: none;
+    margin: 0;
+    padding: 0;
+  }
+
+  .file-btn {
+    display: block;
+    width: 100%;
+    padding: 0.2rem 0.5rem;
+    background: transparent;
+    border: none;
+    color: var(--ctp-subtext0);
+    font-size: 0.72rem;
+    text-align: left;
+    cursor: pointer;
+    transition: color 0.1s, background 0.1s;
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+  }
+
+  .file-btn:hover {
+    background: var(--ctp-surface0);
+    color: var(--ctp-text);
+  }
+
+  .file-btn.active {
+    background: var(--ctp-surface0);
+    color: var(--ctp-text);
+    font-weight: 600;
+  }
+
+  .file-btn.priority {
+    color: var(--ctp-blue);
+  }
+
+  .doc-content {
+    flex: 1;
+    overflow: auto;
+    min-width: 0;
+  }
+
+  .state-msg {
+    color: var(--ctp-overlay0);
+    font-size: 0.75rem;
+    padding: 0.75rem 0.5rem;
+    text-align: center;
+  }
+
+  .state-msg.full {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    height: 100%;
+  }
+</style>