#23672: fix(resilience): guard JSON.parse of external process output with try-catch

## Summary - Problem: `JSON.parse` calls parsing external process stdout (tailscale CLI) and disk-persisted queue entries lack try-catch protection, causing unhandled crashes on malformed input - Why it matters: External process output can be truncated, contain non-JSON preamble text, or be corrupted on disk — all of which cause `SyntaxError` that crashes the gateway - What changed: Added try-catch guards around `JSON.parse` in `parseTailscaleStatusIPv4s()` (bonjour-discovery.ts) and `failDelivery()` (delivery-queue.ts), returning safe fallback values on parse failure - What did NOT change: Happy-path behavior is identical; only error recovery is added ## Change Type - [x] Bug fix ## Scope - [x] Gateway / orchestration ## Security Impact - New permissions/capabilities? No - Secrets/tokens handling changed? No - New/changed network calls? No - Command/tool execution surface changed? No - Data access scope changed? No ## Compatibility / Migration - Backward compatible? Yes - Config/env changes? No - Migration needed? No ## Risks and Mitigations - Risk: Silent failure on corrupted data could mask underlying issues - Mitigation: These are recovery paths where the alternative is a process crash; the calling code already handles empty/null returns gracefully <!-- greptile_comment --> <h3>Greptile Summary</h3> Added defensive `JSON.parse` guards for external process output in two critical paths: Tailscale CLI output parsing (`parseTailscaleStatusIPv4s` in bonjour-discovery.ts:124-130) and disk-persisted delivery queue entries (`failDelivery` in delivery-queue.ts:128-136). Both return safe fallback values (empty array/early return) on parse failure instead of crashing. - **bonjour-discovery.ts**: `parseTailscaleStatusIPv4s()` now catches malformed/truncated JSON from `tailscale status --json` and returns empty array, preventing gateway crashes during Tailnet discovery fallback - **delivery-queue.ts**: `failDelivery()` catches corrupted queue JSON and exits silently, preventing crashes during delivery retry attempts - Test coverage is comprehensive, verifying both truncated JSON and missing files are handled gracefully - Existing `loadPendingDeliveries()` already had similar protection (line 176), so this brings `failDelivery()` to parity <h3>Confidence Score: 5/5</h3> - Safe to merge with no concerns - defensive error handling added to prevent crashes from malformed external data - Changes are minimal, focused, and follow established error-handling patterns in the codebase (see `loadPendingDeliveries` at line 176 for similar try-catch with graceful skip). Test coverage is comprehensive and verifies the exact failure scenarios. Both changes preserve happy-path behavior while adding critical crash prevention for external/disk data parsing. - No files require special attention _{Last reviewed commit: 1bc2470} <!-- greptile_other_comments_section --> _{(5/5) You can turn off certain types of comments like style [here](https://app.greptile.com/review/github)!} <!-- /greptile_comment -->