fix(pi-claude-cli): unblock parameterless MCP tool calls in triage

Triage with claude-sonnet-4-6 via pi-claude-cli kept looping on
fn_review_spec calls that were rejected by pi's validator with
"root: must be object". Parameterless MCP tools (schema
{type:"object", properties:{}}) emit zero input_json_delta events,
so partialJson stayed "" and the catch fell through to
finalArgs = "" — a string, which TypeBox's Type.Object({}) rightly
refuses. Default empty partialJson to {} so the call lands.

Also:
- Add a 2-step reminder loop in triage before swapping to the
  fallback planning model — primary models that wrote PROMPT.md
  but forgot fn_review_spec recover from a nudge, no need to pay
  the cold-start tax of a new triage on a different model.
- Inject @runfusion/fusion's own pi extension into dashboard/
  daemon/serve sessions and propagate the path to createFnAgent
  via setHostExtensionPaths so fn_* tools register globally
  without requiring `pi install npm:@runfusion/fusion`.
- Drop the "historical" qualifier from replayed tool labels —
  Claude was reading "TOOL RESULT (historical Read):" as
  "previous session, ignore" and looping on verification.
- Remove subprocess-lifecycle stderr debug logs that landed for
  hang diagnosis — root cause is fixed, the noise can go.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/pi-claude-cli/src/event-bridge.ts

@@ -323,13 +323,24 @@ export function createEventBridge(
         partial: output,
       });
     } else if (block.type === "tool_use") {
-      // Final JSON parse with fallback to raw string
+      // Final JSON parse with fallback to raw string.
+      // Special case: parameterless MCP tools (e.g. fn_review_spec, schema
+      // `{type:"object", properties:{}}`) emit ZERO input_json_delta events,
+      // so `partialJson` stays "". Without this guard we'd JSON.parse("")
+      // → throw → fall through to `finalArgs = ""` (raw string), and pi's
+      // TypeBox validator then rejects with "root: must be object" because
+      // an empty string is not an object. Default to `{}` so the call lands.
       let finalArgs: Record<string, unknown> | string;
-      try {
-        const parsed = JSON.parse(block.partialJson);
-        finalArgs = translateClaudeArgsToPi(block.claudeName, parsed);
-      } catch {
-        finalArgs = block.partialJson;
+      const trimmedJson = block.partialJson.trim();
+      if (trimmedJson === "") {
+        finalArgs = {};
+      } else {
+        try {
+          const parsed = JSON.parse(trimmedJson);
+          finalArgs = translateClaudeArgsToPi(block.claudeName, parsed);
+        } catch {
+          finalArgs = block.partialJson;
+        }
       }
 
       // Update output.content with final arguments