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

tests/client/session-list-item.test.ts

@@ -151,7 +151,7 @@ describe('SessionListItem', () => {
     })
 
     const logo = wrapper.get('.session-item-agent-logo')
-    expect(logo.attributes('src')).toBe('/coding-agents/hermes.png')
+    expect(logo.attributes('src')).toBe('/logo.png')
     expect(logo.attributes('alt')).toBe('Hermes')
     expect(wrapper.find('.session-item-agent-name').exists()).toBe(false)
   })
@@ -159,7 +159,7 @@ describe('SessionListItem', () => {
   it('defaults old sessions without agent metadata to the Hermes logo', () => {
     const wrapper = mount(SessionListItem, {
       props: {
-        session: { ...session, source: undefined, agent: undefined, codingAgentId: undefined },
+        session: { ...session, source: undefined, agent: undefined },
         active: false,
         pinned: false,
         canDelete: true,
@@ -172,50 +172,8 @@ describe('SessionListItem', () => {
     })
 
     const logo = wrapper.get('.session-item-agent-logo')
-    expect(logo.attributes('src')).toBe('/coding-agents/hermes.png')
+    expect(logo.attributes('src')).toBe('/logo.png')
     expect(logo.attributes('alt')).toBe('Hermes')
     expect(wrapper.find('.session-item-agent-name').exists()).toBe(false)
   })
-
-  it('renders the Claude Code logo for Claude coding agent sessions', () => {
-    const wrapper = mount(SessionListItem, {
-      props: {
-        session: { ...session, source: 'coding_agent', agent: 'claude', codingAgentId: 'claude-code' },
-        active: false,
-        pinned: false,
-        canDelete: true,
-      },
-      global: {
-        stubs: {
-          ProfileAvatar: true,
-        },
-      },
-    })
-
-    const logo = wrapper.get('.session-item-agent-logo')
-    expect(logo.attributes('src')).toBe('/coding-agents/claude-code.svg')
-    expect(logo.attributes('alt')).toBe('Claude Code')
-    expect(wrapper.find('.session-item-agent-name').exists()).toBe(false)
-  })
-
-  it('renders the Codex logo for Codex coding agent sessions', () => {
-    const wrapper = mount(SessionListItem, {
-      props: {
-        session: { ...session, source: 'coding_agent', agent: 'codex', codingAgentId: 'codex' },
-        active: false,
-        pinned: false,
-        canDelete: true,
-      },
-      global: {
-        stubs: {
-          ProfileAvatar: true,
-        },
-      },
-    })
-
-    const logo = wrapper.get('.session-item-agent-logo')
-    expect(logo.attributes('src')).toBe('/coding-agents/codex-openai.png')
-    expect(logo.attributes('alt')).toBe('Codex')
-    expect(wrapper.find('.session-item-agent-name').exists()).toBe(false)
-  })
 })