fleet-ops: require docs-check on every active repo

[cpitzi]

Maps the docs-check / docs-check context across all fifteen active repos, completing the fleet-wide rollout of the reusable from shared-workflows#28 and closing the gap #57 described: docs-only PRs merging having asserted nothing about the docs they changed.

The context string is captured from live check-runs on all fifteen adoption PRs rather than derived from the caller job id, per the standing warning in this file that context names are not display names.

Coverage goes from 11 of 15 to 15 of 15, and the "intentionally unmapped" set is now empty. Adopting docs-check is what closed the last four. brasenia, reference-checker and repo-template previously had only advisory claude workflows and so had no context that could be required. shared-workflows was a structural exception rather than an oversight: every workflow in it is a workflow_call reusable, so nothing had ever run on its own PRs — it now dogfoods docs-check against its own markdown through a local path ref, which additionally means a change that breaks the resolver fails its own pull request.

For the eleven already-mapped repos the new context is added alongside their existing ones; nothing was removed. .github is the exception worth noting: its local relative-link check was deleted in #67 and replaced by this shared one, so the fleet has a single link resolver instead of two copies drifting apart.

A defect surfaced during the rollout and is worth recording here, since this file is where the deadlock-class traps are documented. Every one of the thirteen cross-repo callers failed on first run while the self-caller passed; the reusable resolved its tooling checkout from github.workflow_ref, which is the entry workflow rather than the reusable, so external callers handed their own PR ref to a checkout of shared-workflows and got couldn't find remote ref refs/pull/N/merge. Fixed in shared-workflows#30 by using github.job_workflow_ref. The failure is invisible to self-referential testing, which is why it survived review and merge — worth remembering when the next reusable ships.

The enforcing fleet-apply.sh --require-checks run follows once this merges.