feat: Sprint 17 -- workspace breadcrumbs, slash commands, send key setting

Track A: Workspace breadcrumb navigation
- Breadcrumb path bar with clickable segments when inside subdirectories
- Up button in panel header for parent directory navigation
- S.currentDir state tracking; file ops stay in current directory
- New file/folder creation respects current subdirectory

Track B: Slash commands foundation
- New commands.js module (7th JS module) with command registry and parser
- Built-in commands: /help, /clear, /model, /workspace, /new
- Autocomplete dropdown on / input with arrow/tab/enter/escape navigation
- Unrecognized commands pass through to agent normally

Track C: Send key setting (closes #26)
- send_key added to settings defaults in api/config.py
- Settings panel dropdown: Enter (default) vs Ctrl/Cmd+Enter
- Keydown handler rewritten for autocomplete + send key preference
- Setting loaded on boot, persisted to settings.json

5 new tests, 242 total (219 passing, 22 pre-existing failures, 0 regressions).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

static/style.css

@@ -205,6 +205,13 @@
   .file-action-btn{width:20px;height:20px;background:rgba(0,0,0,.4);border:none;border-radius:4px;color:var(--muted);cursor:pointer;font-size:11px;display:flex;align-items:center;justify-content:center;}
   .file-action-btn:hover{color:var(--accent);}
   .close-preview{cursor:pointer;opacity:.6;}.close-preview:hover{opacity:1;}
+  /* Breadcrumb navigation */
+  .breadcrumb-bar{display:flex;align-items:center;gap:2px;padding:6px 12px;font-size:12px;border-bottom:1px solid var(--border);flex-shrink:0;overflow:hidden;white-space:nowrap;}
+  .breadcrumb-seg{padding:1px 3px;border-radius:3px;}
+  .breadcrumb-link{color:var(--muted);cursor:pointer;transition:color .12s;}
+  .breadcrumb-link:hover{color:var(--text);background:rgba(255,255,255,.06);}
+  .breadcrumb-current{color:var(--text);font-weight:500;}
+  .breadcrumb-sep{color:var(--border);margin:0 1px;font-size:11px;}
   .file-tree{flex:1;overflow-y:auto;padding:8px;}
   .file-item{display:flex;align-items:center;gap:6px;padding:6px 10px;border-radius:7px;cursor:pointer;font-size:12px;color:var(--muted);transition:all .12s;min-width:0;}
   .file-item:hover{background:rgba(255,255,255,.07);color:var(--text);}
@@ -297,6 +304,14 @@
 .ws-row-actions{display:flex;gap:4px;flex-shrink:0;}
 .ws-action-btn{padding:4px 9px;border-radius:6px;font-size:11px;font-weight:600;border:1px solid var(--border2);background:rgba(255,255,255,.05);color:var(--muted);cursor:pointer;transition:all .15s;white-space:nowrap;}
 .ws-action-btn:hover{background:rgba(255,255,255,.1);color:var(--text);}
+/* ── Slash command autocomplete dropdown ── */
+.cmd-dropdown{display:none;position:absolute;bottom:100%;left:0;right:0;background:#1a2535;border:1px solid var(--border2);border-radius:10px;box-shadow:0 -8px 24px rgba(0,0,0,.4);z-index:200;max-height:240px;overflow-y:auto;margin-bottom:4px;}
+.cmd-dropdown.open{display:block;}
+.cmd-item{padding:8px 14px;cursor:pointer;transition:background .12s;}
+.cmd-item:hover,.cmd-item.selected{background:rgba(255,255,255,.07);}
+.cmd-item-name{font-size:13px;color:var(--text);font-weight:500;}
+.cmd-item-arg{color:var(--muted);font-weight:400;font-style:italic;}
+.cmd-item-desc{font-size:11px;color:var(--muted);margin-top:1px;}
 .ws-action-btn.danger:hover{background:rgba(233,69,96,.12);color:var(--accent);border-color:rgba(233,69,96,.3);}
 .ws-add-row{display:flex;gap:8px;align-items:center;padding:10px 0 4px;}
 /* ── Message action buttons (copy, edit, retry) ── */
@@ -352,7 +367,7 @@
 .msg-role > span{line-height:1;}
 
 /* Composer wrap: slightly less padding on smaller heights */
-.composer-wrap{border-top:1px solid rgba(255,255,255,.07);padding:10px 20px 14px;}
+.composer-wrap{border-top:1px solid rgba(255,255,255,.07);padding:10px 20px 14px;position:relative;}
 
 /* Cron status badges: pill shape refinement */
 .cron-status{border-radius:99px;font-size:10px;letter-spacing:.04em;}