fix(agent): register ph-explore for shared claude sessions

[tatoalo]

Problem

Cloud task runs can use the shared Claude session setup, but ph-explore was only registered in a desktop-specific path. That meant the Explore rewrite could target an agent type that was not available for the current session, causing runs to fail when that subagent path was selected.

Changes

• moved the ph-explore agent definition into shared Claude session code so it is registered consistently across envs
• updated session option construction to merge shared default agents with caller-provided agents while still allowing explicit overrides
• removed the duplicate desktop-only wiring and added regression coverage to ensure rewrite targets stay registered in session options.

[greptile-apps]

Prompt To Fix All With AI

This is a comment left during a code review.
Path: packages/agent/src/adapters/claude/session/options.test.ts
Line: 23-36

Comment:
**Prefer parameterised test for rewrite registration**

The test iterates over `SUBAGENT_REWRITES` entries in a for-loop inside a single `it`, which obscures which rewrite entry is failing when the assertion fires. Using `it.each` makes each rewrite a named test case and satisfies the project's preference for parameterised tests.

```suggestion
  it.each(Object.entries(SUBAGENT_REWRITES))(
    'registers rewrite target "%s" → "%s" in options.agents',
    (_source, target) => {
      const options = buildSessionOptions(makeParams());
      const registered = new Set(Object.keys(options.agents ?? {}));
      expect(
        registered.has(target),
        `Rewrite target "${target}" is not registered in options.agents — either register the agent in DEFAULT_CLAUDE_AGENTS or remove the rewrite.`,
      ).toBe(true);
    },
  );
```

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How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (1): Last reviewed commit: "fix(agent): register ph-explore for shar..." | Re-trigger Greptile}