Function sanitize 

pub fn sanitize(raw: &str) -> Option<String>

Reduce a raw model answer to a storable title, or reject it.

Pure, total, and network-free, so it is the part of this module that a unit test can pin exactly.

The rules, in order (each one is load-bearing; the order is the contract)

1. Trim leading/trailing whitespace.
2. First line only — everything from the first \n (or \r) on is dropped, so a chatty answer (“Sure!\n\nSession title: …”) yields its first line, not a paragraph.
3. Strip quotes and backticks — remove every ", ' and ` from what remains (altogether, not just at the ends: a model often returns `w031 session titles`). Interior apostrophes therefore go too; a title is not prose and “don’t” reads fine as “dont” in a one-line label.
4. Collapse whitespace — every run of spaces/tabs becomes one space, so a tab-separated answer cannot break the single-line picker row.
5. Trim again (step 3/4 can expose new edge whitespace).
6. Reject empty — None, never Some(""). This is the ONE place an unusable answer is distinguished from a usable one; a caller that gets None must treat it as “no title”, not as an error to surface.
7. Clamp to TITLE_CLAMP chars, on a char boundary, then trim once more. No ellipsis: a truncated name is still a name, and … would be stored in the transcript forever.

Does not

• Strip a leading Title: / Session: label. Not in W031’s rule list; a model that emits one keeps it (see the module friction note in the loop sketch). Adding it is a later, tested change.
• Reject a long answer — it clamps instead.
• Normalize case, punctuation, or emoji.

Panics

Never. A string of any content (invalid UTF-8 cannot reach here: &str).