Replace generic Error with DaemonConflictError in split-brain guard

[Copilot]

CodeFactor identified the split-brain guard throwing a generic Error instead of a typed exception, preventing callers and tests from distinguishing daemon conflicts from other failure modes.

Changes

• Added DaemonConflictError class in src/core/errors.ts:

  • Extends CodexSynapticError with DAEMON_CONFLICT error code
  • Marked non-retryable (conflicts require operator intervention)
  • Captures structured context: daemonPid, alreadyRunning, allowLocalWithDaemon

• Updated split-brain guard in src/cli/index.ts:

  • Replaced throw new Error(...) with throw new DaemonConflictError(...)
  • Added context object for debugging and telemetry

Example

// Before
throw new Error(`Background daemon already running (pid ${background.pid})...`);

// After
throw new DaemonConflictError(
  `Background daemon already running (pid ${background.pid})...`,
  {
    daemonPid: background.pid,
    alreadyRunning,
    allowLocalWithDaemon: process.env.CODEX_ALLOW_LOCAL_WITH_DAEMON
  }
);

// Now testable via instanceof
try {
  await useSystem('operation', async (sys) => { ... });
} catch (e) {
  if (e instanceof DaemonConflictError) {
    // Handle daemon conflict specifically
  }
}

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[github-actions]

Codex PR Review

Findings

• P3: The split-brain guard now throws DaemonConflictError, but there is no automated coverage to lock this in. A future refactor could silently revert to a generic Error. Adding a targeted test would prevent that regression (src/cli/index.ts:601).

Suggested Fixes

• Add a CLI/system test that stubs getBackgroundStatus() to report an active daemon and asserts useSystem() rejects with DaemonConflictError when CODEX_ALLOW_LOCAL_WITH_DAEMON is unset.

MCP Usage

• deepwiki: Attempted resources/list; failed because DEEPWIKI_API_KEY is unset.
• context7: Attempted resources/list; server responded “Method not found”.
• brave: Attempted resources/list; MCP handshake failed (connection closed).
• jina: Attempted resources/list; failed because JINA_API_KEY is unset.
• firecrawl: Attempted resources/list; MCP handshake failed (connection closed).