AudioRecord: add PASS/FAIL/SKIP exit codes, fix ShellCheck, multiline, platform log

- Return distinct exit codes (0=PASS, 1=FAIL, 2=SKIP) to align with harness.
- Fix ShellCheck issues: SC1091 (sourcing), SC1010 (‘; then’), SC2124 (rc=0).
- Expand one-liners to multi-line for readability; no behavioral changes.
- Log platform details via detect_platform (with safe fallback to ‘unknown’).

Signed-off-by: Srikanth Muppandam <[email protected]>

Author: smuppand