Agent UX: linked tests cannot be edited in place; changing a note means remove + re-add, which reorders indexes and drops provenance

[unbraind]

Problem

A linked test's metadata (note, timeout_seconds, path, scope) cannot be changed in place. The only route is to remove the entry and re-add it:

pm test pm-github-9cjx --remove-index 1
pm test pm-github-9cjx --add-json '{"command":"npm run coverage","path":"scripts/coverage-gate.ts","scope":"project","timeout_seconds":900,"note":"Exact 100/100/100/100 gate …"}'

That has real costs for agents keeping trackers accurate:

• The agent must restate every field. A forgotten path or timeout_seconds is silently dropped.
• The entry moves to the end of --list order, so a later --only-index N or --remove-index N in a script or prompt now targets a different test.
• The original provenance (author, created_at, source_ref) is replaced by the editor's. The record of who linked the test, and when, is lost.
• History shows a removal plus an addition rather than an edit, which reads as a different test.

This came up in a code review: a reviewer bot flagged that a linked test note still said "this item remains open until it measures … exact 100" after the gate passed. Notes like this go stale whenever work completes, and every tracker hygiene pass has to work around it.

Proposal

pm test <id> --update <selector> --set note=… [--set timeout_seconds=…], or --update-index <n> --note …, that:

• edits only the named fields, keeping position and the original provenance, plus an updated_by / updated_at pair;
• records one test_updated history event with a field-level diff;
• refuses selectors that match zero or several entries, with the candidates listed (like --remove);
• has an SDK equivalent (updateLinkedTest) so extensions can maintain their own receipts.

Acceptance

• Changing a note keeps the entry's --list index and original provenance.
• History shows a single update event naming the changed fields.
• An ambiguous or empty selector is refused, with no mutation.

[unbraind]

Canonical tracking: pm-gh1381 — stable metadata entry identity and selective fragment resolution. The complete proposal is retained there as a concrete linked-test editing fixture, preserving position/original provenance, explicit editor metadata, atomic history and unambiguous selectors through a shared SDK primitive. Existing pm-bjpo covers whole-collection replacement; that differs from this entry-preserving edit. No duplicate PM item was created. The feature remains open and unclaimed; PR #1421 records intake without claiming this future editor is implemented.