fix: fence Journal originals before publication and reconcile removal intent

Protect attributed originals before the first public commit; distinguish pending Session material from missing committed sources. Gate removal admission by the Journal Feature and resolve Subject ownership from durable singleton authority. Resume explicit erasure through signed delete transport and proof-bound purge plans without creating a Journal Job or archive.

Validation: changed-crate suites, root check, doc/fmt/diff/naming checks, Server/Runtime builds and worker_environment isolation suite passed. Public standalone scripted dialog connects Host, automatic Job, sequential tools and drain while dialog continues. Backend public embedded WorkerRemove tests connect removal forwarding, durable Jobs, retention, Runtime and SQLite; Session/attribution/profile fixture setup bypasses creation/auth routes. Runtime signed generated-client tests separately exercise request authentication.

Limits: real-model semantic acceptance condition 6 remains unevaluated without a new explicit model/credential/budget grant. Conditions 1/7/8/11 do not have complete product E2E coverage: worker_environment only verifies isolated startup/connection/cleanup. Compaction tests connect local hooks/reader/store rather than the full public dialog-to-Journal chain. Erasure racing a previously prepared Archive removal plan fails closed with conflict; automatic stale-plan replacement is not implemented.

crates/subjektiv/src/journal/mod.rs

@@ -62,6 +62,25 @@ pub const MAX_JOURNAL_READ_BYTES: usize = 16 * 1024;
 /// Whole pretty-serialized public page budget, including escaped text and metadata.
 pub const MAX_JOURNAL_RESPONSE_BYTES: usize = 64 * 1024;
 
+/// Stable owner of Backend source retention, shared by attribution-time protection
+/// and later source admission/release. This identifier confers no read authority.
+/// Local standalone storage uses its scope-exclusive Session UUID as the owner.
+pub fn source_retention_pin(workspace: &str, subject: &str, session: &str) -> Uuid {
+    use sha2::{Digest, Sha256};
+    let digest = Sha256::digest(
+        serde_json::to_vec(&(
+            "subjektiv-journal-retention-v1",
+            workspace,
+            subject,
+            session,
+        ))
+        .expect("string tuple serialization"),
+    );
+    let mut bytes = [0; 16];
+    bytes.copy_from_slice(&digest[..16]);
+    Uuid::from_bytes(bytes)
+}
+
 #[derive(Debug, thiserror::Error)]
 pub enum JournalError {
     #[error("journal permission denied: {0}")]