Enhance std_run execution policy

[codeforester]

Summary

• Add std_run --timeout, --max-attempts, --retry-attempts, and --retry-delay policy options.
• Keep std_run_with_timeout as a compatibility wrapper over the new timeout policy.
• Update docs, changelog, and cookbook example to make std_run --timeout the recommended timeout API.
• Clean up the existing BATS std_function_exists assertion pattern so touched tests pass ShellCheck.

Semantics

• --timeout N is per attempt and returns status 124 with --no-exit.
• --max-attempts N means total attempts; default remains 1.
• --retry-delay N sleeps between failed attempts; default remains 0.
• --retry-attempts is accepted as an alias, but docs recommend --max-attempts.

Validation

• RED: bats lib/bash/std/tests/lib_std.bats failed on the new std_run policy tests before implementation.
• shellcheck --severity=error lib/bash/std/lib_std.sh lib/bash/std/tests/lib_std.bats examples/cookbook-cleanup-temp.sh
• bats lib/bash/std/tests/lib_std.bats
• ./tests/validate.sh
• Verified /Users/rameshhp/work/base has no std_run_with_timeout call sites.

Closes #88