feat(telemetry): use PostHog Error Tracking with $exception events (#3245)

* feat(telemetry): use PostHog Error Tracking with $exception events

Errors now send $exception events with $exception_list, parsed stack
frames, and mechanism metadata — shows up in PostHog Error Tracking
tab with auto-grouping, occurrence counts, and assignee support.
Warnings stay as custom cli_warning events in Activity.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: remove stderr monkey-patch, restore explicit capture calls

Remove process.stderr.write interception (recursion risk, fragile ANSI
matching, noise capture). Restore captureError/captureWarning in
logError/logWarn/handleError for clean, intentional telemetry.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: spawn-bot <spawn-bot@openrouter.ai>

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openrouter/spawn",
-  "version": "0.32.1",
+  "version": "0.32.2",
   "type": "module",
   "bin": {
     "spawn": "cli.js"