Fix black formatting and target Python 3.12 in CI

Reformat 8 files and add --target-version py312 to avoid
3.13 AST parsing issues with Python 3.12 container.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/soosef/federation/chain.py

@@ -433,9 +433,7 @@ class ChainStore:
             if prev_record is not None:
                 expected_hash = compute_record_hash(prev_record)
                 if record.prev_hash != expected_hash:
-                    raise ChainIntegrityError(
-                        f"Record {record.chain_index}: prev_hash mismatch"
-                    )
+                    raise ChainIntegrityError(f"Record {record.chain_index}: prev_hash mismatch")
             elif record.chain_index == 0:
                 if record.prev_hash != ChainState.GENESIS_PREV_HASH:
                     raise ChainIntegrityError("Genesis record has non-zero prev_hash")

src/soosef/fieldkit/deadman.py

@@ -47,9 +47,7 @@ class DeadmanSwitch:
         state["grace_hours"] = grace_hours
         state["last_checkin"] = datetime.now(UTC).isoformat()
         self._save_state(state)
-        logger.info(
-            "Dead man's switch armed: %dh interval, %dh grace", interval_hours, grace_hours
-        )
+        logger.info("Dead man's switch armed: %dh interval, %dh grace", interval_hours, grace_hours)
 
     def disarm(self) -> None:
         """Disarm the dead man's switch."""
@@ -83,9 +81,7 @@ class DeadmanSwitch:
         if not state["armed"] or not state["last_checkin"]:
             return False
         last = datetime.fromisoformat(state["last_checkin"])
-        deadline = last + timedelta(
-            hours=state["interval_hours"] + state["grace_hours"]
-        )
+        deadline = last + timedelta(hours=state["interval_hours"] + state["grace_hours"])
         return datetime.now(UTC) > deadline
 
     def status(self) -> dict:

src/soosef/fieldkit/killswitch.py

@@ -92,14 +92,16 @@ def execute_purge(scope: PurgeScope = PurgeScope.ALL, reason: str = "manual") ->
     ]
 
     if scope == PurgeScope.ALL:
-        steps.extend([
-            ("destroy_auth_db", lambda: _secure_delete_file(paths.AUTH_DB)),
-            ("destroy_attestation_log", lambda: _secure_delete_dir(paths.ATTESTATIONS_DIR)),
-            ("destroy_chain_data", lambda: _secure_delete_dir(paths.CHAIN_DIR)),
-            ("destroy_temp_files", lambda: _secure_delete_dir(paths.TEMP_DIR)),
-            ("destroy_config", lambda: _secure_delete_file(paths.CONFIG_FILE)),
-            ("clear_journald", _clear_system_logs),
-        ])
+        steps.extend(
+            [
+                ("destroy_auth_db", lambda: _secure_delete_file(paths.AUTH_DB)),
+                ("destroy_attestation_log", lambda: _secure_delete_dir(paths.ATTESTATIONS_DIR)),
+                ("destroy_chain_data", lambda: _secure_delete_dir(paths.CHAIN_DIR)),
+                ("destroy_temp_files", lambda: _secure_delete_dir(paths.TEMP_DIR)),
+                ("destroy_config", lambda: _secure_delete_file(paths.CONFIG_FILE)),
+                ("clear_journald", _clear_system_logs),
+            ]
+        )
 
     for name, action in steps:
         try:

src/soosef/keystore/manager.py

@@ -135,9 +135,7 @@ class KeystoreManager:
         from datetime import UTC, datetime
 
         meta_path = self._identity_meta_path()
-        meta_path.write_text(
-            json.dumps({"created_at": datetime.now(UTC).isoformat()}, indent=None)
-        )
+        meta_path.write_text(json.dumps({"created_at": datetime.now(UTC).isoformat()}, indent=None))
 
         return self.get_identity()
 
@@ -263,8 +261,7 @@ class KeystoreManager:
         from datetime import UTC, datetime
 
         (archive_dir / "rotation.txt").write_text(
-            f"Rotated at: {datetime.now(UTC).isoformat()}\n"
-            f"Old fingerprint: {old_fp}\n"
+            f"Rotated at: {datetime.now(UTC).isoformat()}\n" f"Old fingerprint: {old_fp}\n"
         )
 
         new_key = self.generate_channel_key()