fix(pS-usage): fail-safe prune protection — in-wire owner nonce + sticky union poison, protect-all on zero identified, abort on unreadable record, rsusage_ prefix

src/ext_keys.h

@@ -70,17 +70,20 @@ inline constexpr const char* kProjExtBankGenKey = "bank_generation";
 inline constexpr const char* kProjExtAssignKey = "assign_request";
 
 // The pS-usage PER-INSTANCE USAGE-RECORD key prefix. The INSTRUMENT writes one key per
-// instance — "usage_<instanceGuid>" — carrying the sample_usage wire record of every
+// instance — "rsusage_<instanceGuid>" — carrying the sample_usage wire record of every
 // capture that instance holds; the EXTENSION enumerates the prefix at prune-scan time
 // and folds live instances' holds into the prune's `referenced` set so a held capture
 // can never be pruned. This is the ONE sanctioned instrument-side ext-state write
 // (Daniel's ruling — the VST publishes its OWN usage; it never mutates banks/view/
 // tail/assign, and the bridge's write entry point structurally accepts only this
-// prefix). WIRE-SHARED in the write->read direction the other keys reverse. FOREVER-
-// STABLE once shipped: changing the prefix strands every saved project's usage records
-// (prune falls back to bank-references-only until instances republish — graceful, but
-// the instance-hold protection lapses for stale-saved projects).
-inline constexpr const char* kProjExtUsageKeyPrefix = "usage_";
+// prefix). WIRE-SHARED in the write->read direction the other keys reverse. The "rs"
+// qualifier is deliberate: a future key that happens to start with "usage_" must never
+// be swept into the FX-liveness fold (whose abort-on-unreadable rule would then halt
+// every prune), so the prefix is namespaced like the wire magics (rsusage1/rsassign1).
+// FOREVER-STABLE once shipped: changing the prefix strands every saved project's usage
+// records (prune falls back to bank-references-only until instances republish —
+// graceful, but the instance-hold protection lapses for stale-saved projects).
+inline constexpr const char* kProjExtUsageKeyPrefix = "rsusage_";
 
 // The full per-instance usage key for a minted instance GUID (the one composition
 // point, shared by the instrument's writer and the extension's enumerator).