docs(plans): record step 10's merge requests and its moved vocabulary

What this does

Fills step 10's Status row in the S04-A per-format credential columns plan, and adds three files to that step's Files list.

The row was empty while all three of step 10's merge requests were open. Guardrail 4 wants the cell filled at MR-open time from a batch or standing docs(plans) branch, and none of the open ones did it, so a reader could not tell "not yet recorded" from "not started". The row now names !2625 (merged), !2626 (merged) and !2627 (merged) with what each carries, in merge order. Step 3's row already carries two references, so the shape is established in this table.

The Status table stays at eleven rows, so the <step>/11 denominator every step-10 title carries is unchanged.

The Files list also did not mention the three files step 10 moves the refusal vocabulary between. !2626 (merged) created internal/datastore/credential_refusals.go and moved that vocabulary into it out of two Maven files:

• internal/datastore/maven_remote_credentials.go gave up the sentinel, the refusal type, the permanent-refusal list and the marker helper over it, so the list lost its maven prefix in the new file rather than in Maven's.
• internal/datastore/maven_remote_credential_write.go gave up the retired-key discriminator and its warn line, and its two call sites now pass Maven's own constraint name as an argument.

All three files carry a bullet, with line citations pinned to main 9b2540d92, and credential_refusals.go is also named in step 10's "Shared seams", since all three formats' credential reads call through it.

What this leaves alone

Rows 4, 5, 7, 8 and 11 are still empty. Those steps belong to other merge requests and filling them from this branch would guess at references their own authors hold.

Conflict scan

Re-run at 9e09e917f. Of the 71 open merge requests, no other one edits this plan, and git merge-tree against main a9f002cb7 is clean. !2656 (merged), the only other editor the previous scan named, merged on 2026-09-14.