fix(agent-names): use HTTP-header-safe display names and config keys for API calls (#3138)

Display names with parentheses like 'Atlas (Plan Executor)' cause HTTP
header validation errors in x-opencode-agent-name. This was blocking
Atlas/Prometheus from working via /start-work and auto-retry.

Changes:
- Display names: parens -> dashes ('Atlas - Plan Executor')
- Hooks (start-work, no-hephaestus-non-gpt, no-sisyphus-gpt): use
  config keys ('atlas', 'sisyphus', 'hephaestus') for agent API fields
- auto-retry: use config key instead of display name for promptAsync
- agent-override-protection: handle dash-suffix normalization
- Updated all test expectations to match new format

Closes #3138

src/plugin-interface.test.ts

@@ -165,7 +165,7 @@ describe("createPluginInterface - command.execute.before", () => {
     )
 
     // then
-    expect(output.message.agent).toBe(getAgentListDisplayName("atlas"))
+    expect(output.message.agent).toBe("atlas")
     expect(getSessionAgent("ses-command-atlas")).toBe("atlas")
     expect(readBoulderState(testDir)?.agent).toBe("atlas")
   })