feat: add floating help chat widget, remove settings page

Add a documentation-grounded help chat assistant accessible from every
page via a floating button in the bottom-right corner.

Backend (compliance-agent):
- New POST /api/v1/help/chat endpoint
- Loads README.md + docs/**/*.md at first request (OnceLock cache)
- Excludes node_modules, uses walkdir for discovery
- Falls back to degraded prompt if docs not found
- Uses LiteLLM via existing chat_with_messages infrastructure

Dashboard (compliance-dashboard):
- New HelpChat component with toggle button, message area, input
- Styled to match Obsidian Control theme (dark, accent cyan)
- Renders in AppShell so it's available on every page
- Multi-turn conversation with history
- Server function proxies to agent API

Also:
- Remove Settings page (route, sidebar entry, page file)

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

compliance-dashboard/assets/main.css

@@ -3645,3 +3645,205 @@ tbody tr:last-child td {
 .wizard-toggle.active .wizard-toggle-knob {
     transform: translateX(16px);
 }
+
+/* ═══════════════════════════════════════════════════════════════
+   HELP CHAT WIDGET
+   Floating assistant for documentation Q&A
+   ═══════════════════════════════════════════════════════════════ */
+
+.help-chat-toggle {
+    position: fixed;
+    bottom: 24px;
+    right: 28px;
+    z-index: 50;
+    width: 48px;
+    height: 48px;
+    border-radius: 50%;
+    background: var(--accent);
+    color: var(--bg-primary);
+    border: none;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    box-shadow: 0 4px 20px rgba(0, 200, 255, 0.3);
+    transition: transform 0.15s, box-shadow 0.15s;
+}
+.help-chat-toggle:hover {
+    transform: scale(1.08);
+    box-shadow: 0 6px 28px rgba(0, 200, 255, 0.4);
+}
+
+.help-chat-panel {
+    position: fixed;
+    bottom: 24px;
+    right: 28px;
+    z-index: 51;
+    width: 400px;
+    height: 520px;
+    background: var(--bg-secondary);
+    border: 1px solid var(--border-bright);
+    border-radius: 16px;
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+    box-shadow: 0 12px 48px rgba(0, 0, 0, 0.5), var(--accent-glow);
+}
+
+.help-chat-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    padding: 14px 18px;
+    border-bottom: 1px solid var(--border);
+    background: var(--bg-primary);
+}
+.help-chat-title {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    font-family: 'Outfit', sans-serif;
+    font-weight: 600;
+    font-size: 14px;
+    color: var(--text-primary);
+}
+.help-chat-close {
+    background: none;
+    border: none;
+    color: var(--text-secondary);
+    cursor: pointer;
+    padding: 4px;
+    border-radius: 6px;
+    display: flex;
+}
+.help-chat-close:hover {
+    color: var(--text-primary);
+    background: var(--bg-elevated);
+}
+
+.help-chat-messages {
+    flex: 1;
+    overflow-y: auto;
+    padding: 16px;
+    display: flex;
+    flex-direction: column;
+    gap: 12px;
+}
+
+.help-chat-empty {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    height: 100%;
+    text-align: center;
+    color: var(--text-secondary);
+    font-size: 13px;
+    gap: 8px;
+}
+.help-chat-hint {
+    font-size: 12px;
+    color: var(--text-tertiary);
+    font-style: italic;
+}
+
+.help-msg {
+    max-width: 88%;
+    animation: helpMsgIn 0.15s ease-out;
+}
+@keyframes helpMsgIn {
+    from { opacity: 0; transform: translateY(6px); }
+    to { opacity: 1; transform: translateY(0); }
+}
+.help-msg-user {
+    align-self: flex-end;
+}
+.help-msg-assistant {
+    align-self: flex-start;
+}
+.help-msg-content {
+    padding: 10px 14px;
+    border-radius: 12px;
+    font-size: 13px;
+    line-height: 1.55;
+    word-wrap: break-word;
+}
+.help-msg-user .help-msg-content {
+    background: var(--accent);
+    color: var(--bg-primary);
+    border-bottom-right-radius: 4px;
+}
+.help-msg-assistant .help-msg-content {
+    background: var(--bg-elevated);
+    color: var(--text-primary);
+    border: 1px solid var(--border);
+    border-bottom-left-radius: 4px;
+}
+.help-msg-assistant .help-msg-content code {
+    background: rgba(0, 200, 255, 0.1);
+    padding: 1px 5px;
+    border-radius: 3px;
+    font-family: 'JetBrains Mono', monospace;
+    font-size: 12px;
+}
+.help-msg-loading {
+    padding: 10px 14px;
+    border-radius: 12px;
+    background: var(--bg-elevated);
+    border: 1px solid var(--border);
+    border-bottom-left-radius: 4px;
+    color: var(--text-secondary);
+    font-size: 13px;
+    animation: helpPulse 1.2s ease-in-out infinite;
+}
+@keyframes helpPulse {
+    0%, 100% { opacity: 0.6; }
+    50% { opacity: 1; }
+}
+
+.help-chat-input {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding: 12px 14px;
+    border-top: 1px solid var(--border);
+    background: var(--bg-primary);
+}
+.help-chat-input input {
+    flex: 1;
+    background: var(--bg-elevated);
+    border: 1px solid var(--border);
+    border-radius: 8px;
+    padding: 10px 14px;
+    color: var(--text-primary);
+    font-size: 13px;
+    font-family: 'DM Sans', sans-serif;
+    outline: none;
+    transition: border-color 0.15s;
+}
+.help-chat-input input:focus {
+    border-color: var(--accent);
+}
+.help-chat-input input::placeholder {
+    color: var(--text-tertiary);
+}
+.help-chat-send {
+    width: 36px;
+    height: 36px;
+    border-radius: 8px;
+    background: var(--accent);
+    color: var(--bg-primary);
+    border: none;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    transition: opacity 0.15s;
+}
+.help-chat-send:disabled {
+    opacity: 0.4;
+    cursor: not-allowed;
+}
+.help-chat-send:not(:disabled):hover {
+    background: var(--accent-hover);
+}