#5467: Fix: make embedded compaction wait abortable

## Problem When an embedded Pi run is aborted (timeout or an explicit stop), we still await `waitForCompactionRetry()`. If the underlying session never emits the expected compaction/lifecycle events, this await can hang indefinitely. In long-running gateways, that means the teardown path may never run, potentially leaving the session transcript write lock behind and blocking the per-session command lane (e.g. a Discord channel session stops replying). ## Change Wrap the compaction wait with the same abort controller used for the run, so abort/timeout interrupts the wait and teardown proceeds (unsubscribe, clear active run, release session file lock). ## Testing - pnpm vitest run --config vitest.unit.config.ts src/agents/pi-embedded-runner/run/attempt.test.ts - pnpm build <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR makes the post-run compaction wait abortable in the embedded Pi runner. Specifically, the existing `waitForCompactionRetry()` await is now wrapped in the same `runAbortController`-based `abortable(...)` helper used for prompt execution, so an explicit abort/timeout interrupts the compaction wait and allows the teardown path to continue (unsubscribe, clear active run, release session write lock). <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - The change is a single-line behavioral fix that uses an existing, local abort wrapper (`abortable`) already exercised by the prompt code path; it reduces hang risk in teardown and doesn’t alter core session logic beyond making the compaction wait interruptible. - No files require special attention <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->