fix(agent): Send cloud Claude reasoning effort without plugins

[charlesvien]

Problem

Cloud Claude runs configured without plugins silently dropped the selected reasoning effort. effort was nested inside a claudeCode.plugins?.length gate, so plugin-less runs never sent it.

Changes

1. Extract buildClaudeCodeSessionMeta so reasoning effort and plugins are independent
2. Send Claude effort whenever it is set, not only when plugins are present
3. Add tests for effort-only, codex, neither, and plugins+effort combinations

How did you test this?

Manually

Automatic notifications

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[charlesvien]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(agent): Default Codex to the native app-server harness #2723
• fix(agent): Send cloud Claude reasoning effort without plugins #2722 👈 (View in Graphite)
• fix(agent): Preserve Codex base prompt via developer_instructions #2721
• main

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit ad5cb12.}

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
packages/agent/src/server/agent-server.test.ts:1146-1176
**Missing combination test coverage**

The three tests cover the independent cases (effort only, codex-only, neither), but there is no test for the case where both `plugins` and `reasoningEffort` are provided with the `"claude"` adapter. That combination exercises the branch where both `options.plugins` and `options.effort` are populated together — a valid production path that is untested. A fourth case asserting `toEqual({ effort: "high", plugins: [...] })` would close the gap and also let the suite be collapsed into a parameterised table, which is the preferred style in this codebase.

_{Reviews (1): Last reviewed commit: "send claude effort to cloud runs without..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "test claude effort and plugins combinati..." | Re-trigger Greptile}

[github-actions]

Clean bug fix — the old code accidentally gated reasoning effort behind a plugins guard, silently dropping it. The refactor is correct and all branches are covered by the new tests, including the combination case flagged by the bot reviewer.