Diagnostics rc9: process cleanup, reliable reports and Bash 3.2 audit - #14

Problem

The rc8 audit reproduced probe descendants surviving deadlines/cancellation, accepted probe output after a log-write error, final PASS after an incomplete report, a stale profile after option 15 followed by EOF, and a readonly.sh syntax failure in early GNU Bash 3.2.

Changes

• Bound ordinary probe descendants in their own process group; preserve deadline/signal results and reject unfinished work or failed logging.
• Check report input/output failures explicitly, retaining known FAIL evidence and withholding an incomplete final report.
• Save accepted profile restrictions before reading the next menu choice.
• Keep the disk-ID regex in a variable compatible with early Bash 3.2, retaining the existing restriction.
• Add 21 regressions and run them in the existing macOS compatibility workflow without hardware stress.
• Pin the rc9 descriptor and all 18 wrappers to immutable payload/bootstrap a5f95d4; manifest bd9a30dcf4213977366f2bb0c1468acdd97296519155a578b9b82a68c60b9037. Bootstrap 1.4 and registry 2026-09-20.1 are unchanged.

Evidence

• New coherent local full run: 330 tests in 108.278s, OK, no skips (309 existing + 21 new).
• 21 new tests on actual GNU Bash 3.2.0/Linux: OK; 29 shell syntax checks: OK.
• 15 existing native tests with GCC UBSan: OK; small allocations/files only.
• 22 immutable payload files downloaded again and verified; offline toolkit selftest exit 0.
• st.sh ShellCheck warning gate passes. Runtime-wide findings remain 35 SC2034 and 5 SC2209.

See docs/diagnostics/RC9_QA.md for reproductions, exact scope and the menu coverage matrix. Counts from repeated or alternate-shell runs are not added together. Raw logs are retained privately, not included here.

Remaining limits

No real Mac/Recovery, Apple clang, Metal or 40–48 GiB workload validation is claimed. Verified native Recovery binaries are still absent. The diagnostic-fixtures-v1 release returns 404; the fallback remains limited/INCONCLUSIVE. Previous Actions runs did not reach a runner; this PR's CI state must be read independently.

This PR is an audited candidate. The stable main/st.sh command continues to select rc8 until this PR is merged. Mandatory mlock, RAM coverage, volume/consent checks, one-selection/report/exit behavior and RAW quarantine remain in place. VPN/macdiag_core/Yagodka are untouched.