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/fallback.cliproxyapi-matrix.test.ts

@@ -255,7 +255,7 @@ async function primeMainSession(
           content: [],
           modelID: PRIMARY_MODEL.modelID,
           providerID: PRIMARY_MODEL.providerID,
-          agent: "Sisyphus (Ultraworker)",
+          agent: "Sisyphus - Ultraworker",
           path: { cwd: "/tmp", root: "/tmp" },
         },
       },
@@ -337,7 +337,7 @@ async function triggerAssistantMessageError(
           model: PRIMARY_MODEL_STRING,
           modelID: PRIMARY_MODEL.modelID,
           providerID: PRIMARY_MODEL.providerID,
-          agent: "Sisyphus (Ultraworker)",
+          agent: "Sisyphus - Ultraworker",
           path: { cwd: "/tmp", root: "/tmp" },
           error: {
             statusCode: 529,