feat(toolintent): stale-write gate

Block writing a file whose on-disk content changed since the session read it — a
concurrent/external edit the agent's view doesn't reflect. file_read records a
content hash on whole-file reads; the orchestrator's completion path now carries
the tool's structuredOutput (it previously dropped it, unlike SandboxedToolExecutor
— the two paths were inconsistent), so SessionContext.readHashes folds it.
StaleWriteRule compares the current hash (WorldProbe.contentHash) against the
read-time hash and BLOCKs a mismatch, telling the agent to re-read first. Files the
session wrote itself are excluded, so its own edits never look stale; partial reads
set no baseline.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/src/main/kotlin/com/correx/apps/server/Main.kt

@@ -63,6 +63,7 @@ import com.correx.core.toolintent.rules.NetworkHostRule
 import com.correx.core.toolintent.rules.PathContainmentRule
 import com.correx.core.toolintent.rules.ReadBeforeWriteRule
 import com.correx.core.toolintent.rules.ReferenceExistsRule
+import com.correx.core.toolintent.rules.StaleWriteRule
 import com.correx.core.toolintent.rules.WriteScopeRule
 import com.correx.apps.server.freestyle.FreestyleDriver
 import com.correx.apps.server.inference.summarizeWithInference
@@ -269,6 +270,7 @@ fun main() {
             ReadBeforeWriteRule(),
             ReferenceExistsRule(),
             WriteScopeRule(),
+            StaleWriteRule(),
             ManifestContainmentRule(),
             ExecInterpreterRule(toolsConfig.interpreterExecutables.toSet()),
             NetworkHostRule(