docs(release): prepare documented release candidate

docs/IMPLEMENTATION-PLAN.md

@@ -139,13 +139,22 @@ provider-backed agent delegation and skill behavior remain unverified.
 runtime; config collisions are handled or reported before writes; the V2 plugin
 and its custom tool are confirmed active.
 
-### Phase 5 — Document and release (documentation baseline complete)
+### Phase 5 — Document and release (release candidate prepared; publication pending)
 
 - Document scope, installation, update/uninstall, compatibility, provenance,
   and known limitations.
 - Run deterministic checks and security review before release.
 - Confirm package/repository names and get explicit approval before publishing.
 
+**Progress:** README now documents checkout installation, tarball verification,
+update/uninstall behavior, compatibility, and credential-free checks. A manual
+pre-release review of installer paths, ownership, JSONC edits, symlinks, and
+failure behavior found no release blocker for trusted project-local use; its
+filesystem and provider-backed limitations are recorded in
+[`SECURITY-REVIEW.md`](SECURITY-REVIEW.md). Typecheck, all 16 tests, coverage
+(87.4% lines), and package dry-run passed. Publication remains blocked on
+explicit confirmation of the package/repository identity and destination.
+
 **Acceptance:** another user can install from documented instructions and
 verify the deterministic behavior without credentials.