Phase 003: remove the coding-agent and ekko-agent runtimes

Every chat session now runs through the Hermes bridge, so the three chat
chains become feature-equivalent instead of three partially-maintained
dispatch paths. Keeping the coding-agent and in-house agent runtimes alive
meant every bridge change had to be mirrored into two more runtimes that
had already drifted.

Historical rows are read, not migrated: sessions stored with the retired
source normalize to cli on load, workflow graphs naming the retired agents
keep loading and run on the bridge, and the visible-source check plus
SOURCE_LABELS still recognize the old value so those sessions stay listed.

The public surface follows the code: the OpenAPI generator and the MCP
chat-run tool schema drop the six retired entry fields so external callers
are not told about runtimes that no longer exist.

harness-check gains a RETIRED_RUNTIME scan so the residual check is a
mechanical gate instead of a manual grep, with the two surviving read-side
compat sites recorded with reasons.

Refs: docs/phases/phase_003.md

packages/client/src/router/index.ts

@@ -155,11 +155,6 @@ const router = createRouter({
       name: 'hermes.files',
       component: () => import('@/views/hermes/FilesView.vue'),
     },
-    {
-      path: '/hermes/coding-agents',
-      name: 'hermes.codingAgents',
-      component: () => import('@/views/hermes/CodingAgentsView.vue'),
-    },
     {
       path: '/hermes/version-preview',
       name: 'hermes.versionPreview',