markdown-vault-mcp: point STATE_PATH at a file, not the PVC mount dir

Fixes IsADirectoryError on startup when the app tried to atomically
write its change-tracking state to /data/state itself.

clusters/base/apps/markdown-vault-mcp/secret.enc.yaml

@@ -4,19 +4,19 @@ metadata:
     name: markdown-vault-mcp-secrets
     namespace: mcp
 stringData:
-    BEARER_TOKEN: ENC[AES256_GCM,data:YAnKLxac4UuDovt4UGHhw1TxVhpEIpcyGJkfSu7hSDda8j+eNhAlT9ViuffW4TAMR4GAVN62yLHclXwNYkpQIA==,iv:4Bt6kNEV35wrJAuFAMNqzPI+GT2ma0XdEOhNw1LmTXE=,tag:xFh6D177ESEGAswr33fcww==,type:str]
+    BEARER_TOKEN: ENC[AES256_GCM,data:UZ7IAqWz+Vp/Jy023fz31ZYHftSPuDbTqvx1BBMtA+mKQrZ7rPc5ER2sIrjqaUJ04yXHLCnGpud4AWCEZSkJeA==,iv:FYLmyj6DmL/B7b+szRKK53OuWT5YvkMKVgxMDRzwdLc=,tag:jklpeszc+WBNWol+s9VfoA==,type:str]
 sops:
     age:
         - recipient: age1kct5g7d7eus2hvdnmx99ewsrtz70lhlasxa25euqwdctqhwqqpxqz0n7gg
           enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBhcFByU1pHb05mNmFFQXEv
-            bFFPUzd5Zmd5aGd5UFNJRktTbVlOU29OWEEwCmp4eGpZeFpROFpzTG5oN29DbVRl
-            aEJJMXV1RVZRL0Fya21EUjBuOW5OWlEKLS0tIFM1eWxnK2dyclZiTm1FcERtWWlR
-            Mi9acGFhUlE5dlh1blhWcHdHbzBZLzQKdmQ6h3qk7iIa+nOUAayrNV+E1c18d/dR
-            L7pEwJqdqb8uzSBaUzamJBdvBee0NT47qVWLKLgXBat+eiTBUrkK6g==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBSREEzWTdCMGp0U1BjanAv
+            ait2R2lKdlB5dVYxY0oyekZnUDV2WXZTTTJVClp0dWU0VHluT2pFcXBiZnhrRDI1
+            M0VlSDZzWklRcHRCTXQ2N3hiK0pORjQKLS0tIEZyV2VzTDlnS0dLOHZ3SkJTRUVh
+            OG50dFArMUVCbHRaVGR4RkdYVGFZWEkKR5+F1hJJu3HtlYND48U/SABpsEjVQgKa
+            jhxiLrOJ5DBouWDeGVYpWUiYKqTQAcD22YtxkBCFlCJlrCPmdE+Dog==
             -----END AGE ENCRYPTED FILE-----
-    lastmodified: "2026-08-26T10:20:21Z"
-    mac: ENC[AES256_GCM,data:Gb8Er4ZEfovhI8wwvE9HUyd4nXq28dvDO3QSU+fkwRXEHO5tgx7oKFCMFLXuyCZEW6vl2V3Y3unHlRFVEiMyo++hzsYPMz/aLFXbpyhZRIylVHumhOebzYQHa702wMmyFYO5lmVRhpm1WZ8RSiFELLdXd1oZp0j2Qd7+TMt4rhk=,iv:IU5C1lC8m3nbSZyP7C3tjAmYiEZ66PyBUwn8fgPd57k=,tag:b/UWzP+dlKAMsvc93B6yCw==,type:str]
+    lastmodified: "2026-08-26T10:20:26Z"
+    mac: ENC[AES256_GCM,data:l3J8ZQF86r68PPXR3OLtTGoVSpJubAxZO2HkW3w5AS1X2fJu+BtFN0JqGE/cpMOuqqCC96+ADO47IL2HmjW3sVYEib7MY5eZHeOE91x2fwWGOIxNIrTNFu1pJcF3qBQW5NSie82qffH9mXUlX7khzT59TznQX/kk1pYTj8Sdcv8=,iv:neIcdem2MhKxRNSc8HmK6fCpAyFh+pn37MV2qjok/mI=,tag:sl60gLkeUMFrzX6nLK1tkg==,type:str]
     encrypted_regex: ^(data|stringData)$
     version: 3.11.0