fix(observability): tame log defaults + user config override (closes #519) (#686)

iii-observability worker emits a WARN every time its log subscriber falls behind, and that WARN re-enters the same broadcast stream the subscriber is failing to drain — positive feedback loop that wrote 137 GB to ~/.agentmemory/daemon.log.new on one reporter's laptop in a few days. Root cause sits in the iii binary (Rust upstream), but we can mute the trigger surface from this side.

Two changes:
- iii-config.yaml + iii-config.docker.yaml: sampling_ratio 1.0 → 0.1 and logs_console_output true → false. At 0.1 the subscriber catches up under sustained load; with console off, the WARN line that re-feeds the loop never reaches the amplifying layer.
- src/cli.ts findIiiConfig: precedence reversed so the bundled config no longer wins unconditionally. New order: AGENTMEMORY_III_CONFIG env var > project cwd > ~/.agentmemory/iii-config.yaml > bundled. Users who hit the loop on existing installs now have a documented override path that survives npm i -g upgrades.

iii-config.docker.yaml

@@ -40,10 +40,11 @@ workers:
       enabled: true
       service_name: agentmemory
       exporter: memory
-      sampling_ratio: 1.0
+      # See iii-config.yaml for the rationale on 0.1 / console-off (#519).
+      sampling_ratio: 0.1
       metrics_enabled: true
       logs_enabled: true
-      logs_console_output: true
+      logs_console_output: false
   - name: iii-exec
     config:
       watch:

iii-config.yaml

@@ -40,10 +40,19 @@ workers:
       enabled: true
       service_name: agentmemory
       exporter: memory
-      sampling_ratio: 1.0
+      # 0.1 instead of 1.0: at full sampling under sustained load the
+      # log subscriber falls behind, the worker emits a "Log trigger
+      # subscriber lagged" WARN, and that WARN re-enters the same
+      # stream the subscriber is failing to drain — a positive
+      # feedback loop that wrote 137 GB to daemon.log.new on one user
+      # in a few days (#519).
+      sampling_ratio: 0.1
       metrics_enabled: true
       logs_enabled: true
-      logs_console_output: true
+      # Console output is off by default; the feedback path needs the
+      # console layer to amplify. Re-enable per-session via env if you
+      # need verbose tracing for debugging.
+      logs_console_output: false
   - name: iii-exec
     config:
       watch:

src/cli.ts

@@ -302,10 +302,18 @@ async function isAgentmemoryReady(): Promise<boolean> {
 }
 
 function findIiiConfig(): string {
+  // Precedence (user-overridable wins): explicit env > project cwd >
+  // ~/.agentmemory/ > bundled. The bundled config used to win
+  // unconditionally, so users hitting the observability log-feedback
+  // loop (#519) had no way to drop a tamer config in place without
+  // editing node_modules.
+  const envPath = process.env["AGENTMEMORY_III_CONFIG"];
   const candidates = [
+    ...(envPath ? [envPath] : []),
+    join(process.cwd(), "iii-config.yaml"),
+    join(homedir(), ".agentmemory", "iii-config.yaml"),
     join(__dirname, "iii-config.yaml"),
     join(__dirname, "..", "iii-config.yaml"),
-    join(process.cwd(), "iii-config.yaml"),
   ];
   for (const c of candidates) {
     if (existsSync(c)) return c;