fix: apply the review items for #708 at merge

- test/cli-agent-project-spawn.test.ts:345: the doc-sync test no longer reads .changeset/project-worker-directories.md (changeset version deletes it at release); README, API reference and wiki stay.
- CLAUDE.md:132 + src/cli-agent.ts @fileoverview (invariant 5): the directory spawn (POST /api/v1/sessions plus /interactive or /shell, no Agent-Origin header, so no marker) and its refusals (empty --working-dir, bare spawn from a HOME cwd); the invariants now name test/cli-agent-project-spawn.test.ts too.
- test/cli-agent-project-spawn.test.ts:322: "allows a cwd below HOME" mocks the cwd to <temp HOME>/src/app, so it covers the case the guard must leave alone.
- docs/wiki/Driving-Codeman-From-An-Agent.md:59: split the sentence so exit 4 covers only the empty --working-dir; spawn "" reaches quick-start and exits 1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/wiki/Driving-Codeman-From-An-Agent.md

@@ -56,9 +56,10 @@ codeman agent rm "$SID"                                   # any session except t
 
 - **`spawn [case]`** uses the current directory when no case is supplied. Use
   `codeman agent spawn --working-dir /path/to/project --mode codex` for another existing
-  local directory. A case and `--working-dir` cannot be combined, and an empty case
-  name (`spawn "$CASE"` with `CASE` unset) is refused rather than read as "no case",
-  as is an empty `--working-dir` (exit 4, before any request), so it never falls back to cwd.
+  local directory. A case and `--working-dir` cannot be combined. An empty case name
+  (`spawn "$CASE"` with `CASE` unset) is never read as "no case": it goes to quick-start,
+  which refuses it (exit 1). An empty `--working-dir` is refused before any request
+  (exit 4), so it never falls back to cwd.
   A cwd that is your home directory is refused the same way, because Codeman's hooks would
   land in `~/.claude`; pass `--working-dir ~` to start a worker there on purpose.
   Explicit case names retain quick-start behavior (creating a scratch case if missing).