fix(flow): refuse an API step whose span also wrote

[abrichr]

Fourth of six fixes from an external review of #1269. Stacked on #1369 (then #1368), because all three change api_proposal.py.

Bug

An earlier write inside the span (for example POST /reserve.php) was only listed in other_writes_seen, and the API step still replaced the whole span. A run therefore skipped that write.

Fix

• Proposal: refused when any POST, PUT, PATCH or DELETE other than the save was sent while the replaced steps ran. The reason names the write.
• Admission: api admit refuses a binding that lists other writes.
• Run: a binding admitted before this rule runs on the GUI, and api_fallback names the write.

Impact on the OpenEMR referral (needs a decision)

This refuses the referral's API step. OpenEMR's background POST /library/ajax/execute_background_services.php lands inside the span:

the steps the API step would replace also sent POST /library/ajax/execute_background_services.php; one request can't stand in for them

That is the rule as asked, and it fails closed. If background polls like this should be allowed, a person would have to declare a recorded write as unrelated at admission. That is a follow-up for the founder; it isn't in this PR.

Tests

tests/test_api_proposal_other_writes.py (new, 7 tests):

• the reviewer's /reserve.php case for POST, PUT, DELETE and PATCH;
• a read inside the span is still fine;
• admission refuses;
• a binding admitted before the rule runs on the GUI with the write named.

54 pass with the API-tier, provenance and URL tests.

Synthetic values only.

🤖 Generated with Claude Code

[abrichr]

Included in batch #1383, which runs CI once for several reviewed PRs. This PR is marked merged when #1383 merges. Please don't push here unless asked; a new commit leaves it out of the batch.