fix(issue-10,13): check every agy artifact for holders and purge orphaned leftovers

Round-3 review of f5a6575 (planner-reviewer-codex-01, R1/R2).

R1 - the adapter's in-use check handed only the conversation DB to lsof, so a
holder that keeps the presence lock (or a sidecar) open while naming the uuid
on no command line and in no session variable was invisible, and the held
lock was unlinked from under it. AgyAgentAdapter.conversation_in_use now
passes every path of the conversation (DB, -wal/-shm/-journal, brain,
annotation, presence lock).

R2 - both resolver stages required the DB, so once an interrupted or pre-#10
purge had removed it, the WAL/annotation/lock left behind were "no artifact"
(exit 5) forever. BaseAgentAdapter.has_artifacts (default: a uuid-bearing
artifact path that exists) replaces the resolver's path fallback, and agy's
override accepts any of its pieces.

Tests: a flock holder that names the uuid nowhere is refused and nothing is
removed; orphaned leftovers resolve to agy and are purged. VERSIONS.md
v4.4.3 items 1-2 and orc-onboard SKILL.md updated.

Refs #10 #13

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/lib_py/agents/base.py

@@ -191,6 +191,14 @@ class BaseAgentAdapter:
         on-disk tree override this; the default has nothing to scan."""
         return []
 
+    def has_artifacts(self, uuid: str, ctx: DiscoveryContext) -> bool:
+        """Anything of this conversation is on disk (a purge target exists
+        even when `verify_artifact` would not vouch for it). The default only
+        trusts an artifact path that embeds the uuid - a shared store (one DB
+        for every conversation) exists for any uuid and proves nothing."""
+        path = self.artifact_path(uuid, ctx)
+        return uuid in path and os.path.exists(path)
+
     def conversation_in_use(self, uuid: str, ctx: DiscoveryContext) -> bool:
         """True while a live process still references the conversation."""
         return conversation_in_use(uuid, [self.artifact_path(uuid, ctx)])