[codex] Clean up terminal-result adapter process groups (#4129)

## Thinking Path

> - Paperclip runs local adapter processes for agents and streams their
output into heartbeat runs
> - Some adapters can emit a terminal result before all descendant
processes have exited
> - If those descendants keep running, a heartbeat can appear complete
while the process group remains alive
> - Claude local runs need a bounded cleanup path after terminal JSON
output is observed and the child exits
> - This pull request adds terminal-result cleanup support to adapter
process utilities and wires it into the Claude local adapter
> - The benefit is fewer stranded adapter process groups after
successful terminal results

## What Changed

- Added terminal-result cleanup options to `runChildProcess`.
- Tracked child exit plus terminal output before signaling lingering
process groups.
- Added Claude local adapter configuration for terminal result cleanup
grace time.
- Added process cleanup tests covering terminal-output cleanup and noisy
non-terminal runs.

## Verification

- `pnpm install --frozen-lockfile --ignore-scripts`
- `pnpm exec vitest run packages/adapter-utils/src/server-utils.test.ts`
- Result: 9 tests passed.

## Risks

- Medium risk: this changes adapter child-process cleanup behavior.
- The cleanup only arms after terminal result detection and child exit,
and it is covered by process-group tests.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex coding agent based on GPT-5, tool-enabled local shell and
GitHub workflow, exact runtime context window not exposed in this
session.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots, or documented why it is not applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

packages/adapters/claude-local/src/server/execute.ts

@@ -330,6 +330,10 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
     graceSec,
     extraArgs,
   } = runtimeConfig;
+  const terminalResultCleanupGraceMs = Math.max(
+    0,
+    asNumber(config.terminalResultCleanupGraceMs, 5_000),
+  );
   const effectiveEnv = Object.fromEntries(
     Object.entries({ ...process.env, ...env }).filter(
       (entry): entry is [string, string] => typeof entry[1] === "string",
@@ -503,6 +507,10 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
       graceSec,
       onSpawn,
       onLog,
+      terminalResultCleanup: {
+        graceMs: terminalResultCleanupGraceMs,
+        hasTerminalResult: ({ stdout }) => parseClaudeStreamJson(stdout).resultJson !== null,
+      },
     });
 
     const parsedStream = parseClaudeStreamJson(proc.stdout);