[RomainROCH]

What this PR does

Run the isolated status scenario in an owned child with a 30-second monotonic polling deadline and a five-second post-kill polling budget. Add PID phase traces, a completion receipt written after fixture destruction, and a separate inert cleanup control.

Base: main at 1b9556222d89419c5e6b28f2bf83f2d6e0b7d4e1. Head: 89722976c56ce678053b573ef9a405fd7b4fa5bb, parent ecd92460c65466caf8989601fdc4edc8db49c133, already merged through PR #9. The requested main target is explicit; the diff contains only tests/status_connection_budget.rs.

Why

Run 38619754062 remained in the isolated status scenario for more than ten minutes and was cancelled to retain its logs. The internal phase and cause remain unknown.

This draft is for diagnostic CI. It changes no production behavior, dependencies, mutex fixture or workflow. A green run alone does not demonstrate a correction. Permanent adoption, merge and release inclusion remain deferred.

The polling budgets do not bound the entire CI job: stderr writes, spawn, file/endpoint operations and termination calls remain synchronous, and Drop may retry cleanup.

How it was tested

• Full checks must pass on the exact CI head; no local aggregate result is claimed on this diagnostic commit.
• Local target passed 9 parent tests plus 1 scenario child; formatting and strict all-targets/all-features Clippy passed on the committed bytes.
• 67 phase lines checked, zero surviving owned test processes, receipts and endpoints cleaned.
• The inert cleanup control passed; it does not reproduce the historical IPC wait or a complete 30-second scenario timeout.
• Developer and smoke safety jobs will be assessed in the exact CI run; their scripts are unchanged.
• No physical-power, elevated relaunch or state-changing local smoke coverage claimed.
• No production contract or architecture change requiring documentation.

Checklist

• Base branch and explicit integration target stated.
• Test-only diagnostic; no intentional architecture or business-model change.
• Existing concurrent work preserved.
• No merge at this stage; review exact CI traces and results first.