[codex] harden heartbeat run summaries and recovery context (#3742)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Heartbeat runs are the control-plane record of what agents did, why
they woke up, and what operators should see next
> - Run lists, stranded issue comments, and live log polling all depend
on compact but accurate heartbeat summaries
> - The current branch had a focused backend slice that improves how run
result JSON is summarized, how stale process recovery comments are
written, and how live log polling resolves the active run
> - This pull request isolates that heartbeat/runtime reliability work
from the unrelated UI and dev-tooling changes
> - The benefit is more reliable issue context and cheaper run lookups
without dragging unrelated board UI changes into the same review

## What Changed

- Include the latest run failure in stranded issue comments during
orphaned process recovery.
- Bound heartbeat `result_json` payloads for list responses while
preserving the raw stored payloads.
- Narrow heartbeat log endpoint lookups so issue polling resolves the
relevant active run with less unnecessary scanning.
- Add focused tests for heartbeat list summaries, live run polling,
orphaned process recovery, and the run context/result summary helpers.

## Verification

- `pnpm vitest run
server/src/__tests__/heartbeat-context-summary.test.ts
server/src/__tests__/heartbeat-list.test.ts
server/src/__tests__/agent-live-run-routes.test.ts
server/src/__tests__/heartbeat-process-recovery.test.ts`

## Risks

- The main risk is accidentally hiding a field that some client still
expects from summarized `result_json`, or over-constraining the live log
lookup path for edge-case run routing.
- Recovery comments now surface the latest failure more aggressively, so
wording changes may affect downstream expectations if anyone parses
those comments too strictly.

## Model Used

- OpenAI Codex, GPT-5-based coding agent in the Codex CLI environment.
Exact backend model deployment ID was not exposed in-session.
Tool-assisted editing and shell execution were used.

## 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 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
- [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

server/src/services/heartbeat-run-summary.ts

@@ -1,4 +1,8 @@
-function truncateSummaryText(value: unknown, maxLength = 500) {
+export const HEARTBEAT_RUN_RESULT_SUMMARY_MAX_CHARS = 500;
+export const HEARTBEAT_RUN_RESULT_OUTPUT_MAX_CHARS = 4_096;
+export const HEARTBEAT_RUN_SAFE_RESULT_JSON_MAX_BYTES = 64 * 1024;
+
+function truncateSummaryText(value: unknown, maxLength = HEARTBEAT_RUN_RESULT_SUMMARY_MAX_CHARS) {
   if (typeof value !== "string") return null;
   return value.length > maxLength ? value.slice(0, maxLength) : value;
 }