[khushalsonawat]

Description

Follow-up to #278, which merged with Dileep's review open. Each of his eight points is answered on its thread. The only code change is his docstring point. The rest are either owned by another open ticket or named as limits:

• A password holding /, ? or # (P1, and the P3 on #/?) is a real leak, which existed before [TH-9491] fix: keep URL credentials in an agent's description out of what the kit sends and stores #278. It is TH-9500's: its rule 1 removes such a password before the address step, with guards that keep honest text like localhost:3000 … support@acme.com intact. TH-9500 (Birch) is in change review now. A cut in _redact_url was tried here. Its review found that it would conflict with rule 1 and needed more guards of its own, so it isn't in this PR.
• //user:pass@host and scheme:\\user:pass@host (P2) are named as a TH-9500 limit. The finder starts an address only at ://, which the streaming chat cleaner shares.
• JSON joined to an address (P2) is a named limit. Every quote-ending rule tested leaked a key. JSON span values are cleaned leaf by leaf in fix(harness): clean every trace span before it leaves for Observe (TH-9504) #280.
• The agent under test runs on the cleaned excerpt (P3). A raw copy would leave the sandbox in the uploaded transcript.
• A public redaction module (P3) comes after fix(harness): clean every trace span before it leaves for Observe (TH-9504) #280, which adds a consumer. It goes in the older-findings register.
• The docstring (P3) is fixed here.

Type of Change

• Documentation

Testing

A docstring-only change to src/fi/alk/harness/contract.py.

Related Issues

Refs: TH-9491