Merge pull request #567: fix(cases): only refuse the cases folder and its direct children for a custom-folder case

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/api-reference.md

@@ -1020,7 +1020,7 @@ The target is judged before anything is written:
 
 - It must be absolute with no `..` and none of the shell metacharacters a session working directory is rejected for (spaces are fine). `400 INVALID_INPUT` otherwise.
 - It must not be a system directory (`/etc`, `/usr`, `/proc`, ...), the home folder itself, Codeman's own data folder, or a credential/config tree (`~/.ssh`, `~/.aws`, `~/.claude`, ...). Judged on the path as typed and on its symlink-resolved form, against both the given and the symlink-resolved roots. `400`.
-- It must not be, or be inside, the cases directory (the caller's own and the shared one): a case there is a plain create without `path`. `400`.
+- It must not be the cases directory (the caller's own or the shared one) or a direct child of it, since those are what `GET /api/cases` lists as local cases: a case there is a plain create without `path`. A folder further down is allowed. `400`.
 - Its parent must already exist (one folder is created, never a chain): `404 NOT_FOUND`. A parent that does not answer (an unreachable network mount) or cannot be read is `422 OPERATION_FAILED`, checked through the bounded path probe before anything else touches it.
 - The folder must not exist, or must be an **empty** directory; a folder with contents is Link Existing's job: `409 ALREADY_EXISTS`. A symlink or a plain file at the target is `400`.
 - `409 ALREADY_EXISTS` also for a case name already in use (in the cases dir or the registry) and for a folder that is already a case.