test: fix weak and near-duplicate assertions in sanitize.rs

[github-actions]

Test Suite Reduction: src/sanitize.rs

What was wrong

• test_sanitize_preserves_markdown_headings: used three weak contains() assertions instead of checking the full output. Critically, assert!(result.contains("#123")) would pass even if the implementation incorrectly wrapped bare #123 in backticks, hiding a regression in the bot-trigger neutralization guard (which should only wrap patterns like fixes #123, not a standalone #123).
• test_sanitize_config_removes_control_chars: used the exact same input and expected value ("hello\x00world\x07!" → "helloworld!") as the unit test test_remove_null_and_bell, making it a near-duplicate that adds no incremental coverage.

Changes

Test	Action	Reason
test_sanitize_preserves_markdown_headings	Rewritten	Weak contains("#123") would pass even on a wrong implementation; replaced with assert_eq! on the full output
test_sanitize_config_removes_control_chars	Rewritten	Near-duplicate of test_remove_null_and_bell; now uses an ANSI escape sequence input (val\x1b[0mue → value) that is distinct from the null/bell test

Verification

• cargo test: all 1660 tests pass ✅
• cargo clippy --all-targets --all-features: no errors ✅

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

• dev.azure.com

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "dev.azure.com"

See Network Configuration for more information.

Generated by Test Reducer · ● 11M · ◷