Phase 005: vendor ArkScope, land the Arco style baseline, and fix bridge interpreter resolution

- Vendor ArkScope decorative layers (ScrambleTitle / IsometricWave) with provenance notes; decorative-only per AGENTS.md red lines
- Migrate theme tokens to Arco, register the Arco theme, and add hook adapter composables (useMessage / useDialog / useNotification) with matching signatures
- Sample pages: LoginView and AppSidebar on the new baseline; docs/arco-mapping.md and docs/ui-baseline.md land
- agent-bridge: prefer the PM-selected venv from facts.json over legacy in-tree venvs (legacy lacks the mcp extra, so every MCP server showed 0 tools / not connected)
- agent-bridge python (vendored, deliberate deviation): MCP discovery import fallback and pyyaml -> hermes_yaml so plugins and MCP work under the PM env; install the mcp extra via `hermes pm install --extra mcp`
- Chat-chain fragment: docs/chat-chain-changes/2026-10-17-phase005-arkscope-baseline.md

Verified: harness:check, test (2020 passed), test:e2e (30 passed), build all green; manual: plugins 100/0 warnings, MCP 6/6 servers connected with 104 tools.

packages/client/src/styles/arco-theme.ts

@@ -0,0 +1,14 @@
+// Arco Design theme tokens for hermes-ui (Phase 005 baseline).
+// Dark mode is carried by `body[arco-theme='dark']` CSS overrides, not a second theme object.
+// See docs/ui-baseline.md for the frozen visual language.
+export const arcoTheme = {
+  // 延续旧版克制灰阶
+  colorPrimary: '#2f2f2f',
+  colorBgLayout: '#fafafa',
+  colorBgContainer: '#ffffff',
+  borderRadius: 6,
+  fontFamily: 'Inter, system-ui, -apple-system, sans-serif',
+  fontFamilyMono: '"JetBrains Mono", "Fira Code", monospace',
+}
+
+export type ArcoTheme = typeof arcoTheme