docs(state-gitignore): slim header for consumer clarity

.changeset/state-gitignore-slim.md

@@ -0,0 +1,18 @@
+---
+"@stainless-code/codemap": patch
+---
+
+Slim the auto-generated `<state-dir>/.gitignore` header for consumer clarity:
+
+- Drop the internal function-name reference (`ensureStateGitignore`) — consumers can't look it up.
+- Drop the "Rule 9 analogue" / "bump alongside any new cache" line — it was guidance for codemap contributors, leaking into every consumer's checkout.
+- Reframe "blacklist" / parenthetical mention of tracked files in plainer language.
+
+Existing two-line header (`# codemap-managed — edits will be overwritten by ensureStateGitignore.` / `# Blacklist of generated artifacts...`) becomes:
+
+```
+# Managed by codemap — overwritten on next run.
+# Generated artifacts only; user-authored config (config.*, recipes/) stays tracked.
+```
+
+**One-time rewrite on consumer side.** The reconciler matches the canonical body via exact string comparison, so every consumer's next `codemap` run rewrites `<state-dir>/.gitignore` to the new shape (no entries change — only the comment lines). Harmless; the blacklist entries (`index.db`, `index.db-shm`, `index.db-wal`, `audit-cache/`) are unchanged.

.codemap/.gitignore

@@ -1,6 +1,5 @@
-# codemap-managed — edits will be overwritten by `ensureStateGitignore`.
-# Blacklist of generated artifacts; tracked sources (recipes/, config.*)
-# default to tracked. Bump alongside any new cache (Rule 9 analogue).
+# Managed by codemap — overwritten on next run.
+# Generated artifacts only; user-authored config (config.*, recipes/) stays tracked.
 index.db
 index.db-shm
 index.db-wal

fixtures/minimal/.codemap/.gitignore

@@ -1,6 +1,5 @@
-# codemap-managed — edits will be overwritten by `ensureStateGitignore`.
-# Blacklist of generated artifacts; tracked sources (recipes/, config.*)
-# default to tracked. Bump alongside any new cache (Rule 9 analogue).
+# Managed by codemap — overwritten on next run.
+# Generated artifacts only; user-authored config (config.*, recipes/) stays tracked.
 index.db
 index.db-shm
 index.db-wal

src/application/state-dir.ts

@@ -48,9 +48,8 @@ export function resolveStateDir(opts: ResolveStateDirOpts): string {
  * the source of truth — header, blank lines, and ordering all reproduce
  * verbatim. Add new generated artifacts in the same PR that introduces them.
  */
-export const STATE_GITIGNORE_BODY = `# codemap-managed — edits will be overwritten by \`ensureStateGitignore\`.
-# Blacklist of generated artifacts; tracked sources (recipes/, config.*)
-# default to tracked. Bump alongside any new cache (Rule 9 analogue).
+export const STATE_GITIGNORE_BODY = `# Managed by codemap — overwritten on next run.
+# Generated artifacts only; user-authored config (config.*, recipes/) stays tracked.
 index.db
 index.db-shm
 index.db-wal