feat(FN-1216): rename extension tools to fn_* across CLI and docs

- Rename all pi extension tool registrations from kb_* to fn_* across task, mission, and agent tool families
- Update extension and skill-sync tests plus Fusion skill docs/workflows to assert and document the new fn_* tool names
- Align product-identity strings across core, dashboard, and CLI references, including GitHub import examples, User-Agent headers, and terminal TERM_PROGRAM
- Add a @gsxdsm/fusion minor changeset describing the extension tool-prefix rename

packages/core/src/agent-store.ts

@@ -76,7 +76,7 @@ type TypedEventEmitter<Events extends Record<string, unknown[]>> = {
 
 /** Options for AgentStore constructor */
 export interface AgentStoreOptions {
-  /** Root directory for kb data (default: .fusion) */
+  /** Root directory for fn data (default: .fusion) */
   rootDir?: string;
 }