fix: reconcile erased Archive removals and exercise live compaction recording

Reconcile immutable Runtime removal input under a confirmed permanent erase fence. A confirmed source_removed receipt is audited without republishing erased archives; unknown receipt plus attested remaining aggregate permits an audited stale plan and proof-bound purge replacement. Unknown receipt and inventory remain unresolved. Distinguish domain tombstones from scoped Runtime physical erasure acknowledgements.

Erase diagnostic originals and interrupted staging bound to the same archived Session/removal operation, validating Workspace/Worker/fingerprint and saved receipts without rewriting their historical retained flags. Finalize Backend removal only after physical acknowledgement, including previous Retain disposition.

Connect public standalone protocol, real Worker request-threshold compaction twice within one turn, cancellation and real pre-AI input rollback, original canonical readers, existing Jobs and sequential Journal tools. Gate generation while compaction completes; verify all durable originals were served, summary/rolled-back input exclusion, exact final cursor, no extra input for successor drain, and one ongoing open entry. External model streams/usage are scripted, not semantic evaluation.

Validation: Backend1112lib+11bin (existing ignore1), Runtime429lib+38bin, standalone72lib+27integration (existing model ignore1), runtime-api10, root check/doc/fmt/diff/naming, Server/Runtime builds, isolated worker_environment2 passed. Earlier broad suites remain recorded on the prior source. Fixtures and injected boundaries are not arbitrary crash/remote-transport-loss coverage; worker_environment only verifies startup/connection/cleanup.

Acceptance clarification: T-734 assignment answer event22 explicitly defers real-model semantic condition6 to user use, excluding it from this completion scope. It remains unexecuted and unevaluated, not passed. Technical review findings still require a fresh independent verdict on this source.

crates/runtime-api/src/lib.rs

@@ -812,6 +812,9 @@ pub struct SessionMaterialEraseRequest {
     pub expected_session_id: String,
 }
 
+/// Acknowledges the permanent fence and physical erasure of Session originals,
+/// including archived diagnostics bound to the same removal operations. Historical
+/// retention receipts remain immutable; their old retained flags are not current availability.
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct SessionMaterialEraseResponse {
     pub session_id: String,