fix: access tool parameters from part.state.input instead of part.parameters

Session message ToolPart stores input in part.state.input, not part.parameters.
When parameters were undefined, all tools of the same type got identical
signatures, causing the deduplicator to incorrectly mark them all as duplicates.

Author: Tarquinen

lib/janitor.ts

@@ -109,7 +109,8 @@ export class Janitor {
                             toolCallIds.push(normalizedId)
 
                             const cachedData = this.toolParametersCache.get(part.callID) || this.toolParametersCache.get(normalizedId)
-                            const parameters = cachedData?.parameters || part.parameters
+                            // Session messages store input in part.state.input, not part.parameters
+                            const parameters = cachedData?.parameters ?? part.state?.input ?? part.parameters
 
                             toolMetadata.set(normalizedId, {
                                 tool: part.tool,