D101 — Tool names in the docs are CI-enforced

Decision. TestDocsToolNamesExist (internal/mcpserver/docs_test.go) scans README.md, AGENTS.md, CONTRIBUTING.md and current-state pages under docs/ for backticked snake_case identifiers carrying an MCP domain prefix (atlas_, concept_, map_, sync_, …) and fails if one is not a registered tool. It builds the full surface to compare against (AllowArtifactWrite, a non-nil BundleFS), since artifact and bundle tools register conditionally. The historical docs/decisions/ directory is excluded, where citing a since-renamed tool is correct. Homonyms that are not tools (lint rules, frontmatter fields, the deliberately absent concept_collapse) live in an explicit docsNonTools allow-list.

Rationale. Two renames (D66 kb_overview→atlas_overview, D77 archive_*/dossier_*→map_*) left dead names in the prose, and both survived until someone read the page by chance: the README was still advertising kb_overview, archive_list and dossier_list — the project's front page listing three tools removed months earlier, while a unit test asserted their removal from the code. Grep-based audits kept missing them because a tool is cited as `name` far more often than as name(. An allow-list is deliberately chosen over a heuristic: adding a legitimate homonym costs one line and a reason, whereas a clever regex silently stops catching things.

Consequences. A rename now fails CI until every page follows, which is the same discipline mkdocs --strict applies to links (D100). Same-session fixes: README §Key features and §Architecture (which still described the pre-D77 archive → dossier → concept hierarchy) and sync.md's description of the generated instructions block — the code emitted atlas_overview correctly, only the doc was stale.