* fix(agents): recognize connection errors as retryable timeout failures
## Problem
When a model endpoint becomes unreachable (e.g., local proxy down,
relay server offline), the failover system fails to switch to the
next candidate model. Errors like "Connection error." are not
classified as retryable, causing the session to hang on a broken
endpoint instead of falling back to healthy alternatives.
## Root Cause
Connection/network errors are not recognized by the current failover
classifier:
- Text patterns like "Connection error.", "fetch failed", "network error"
- Error codes like ECONNREFUSED, ENOTFOUND, EAI_AGAIN (in message text)
While `failover-error.ts` handles these as error codes (err.code),
it misses them when they appear as plain text in error messages.
## Solution
Extend timeout error patterns to include connection/network failures:
**In `errors.ts` (ERROR_PATTERNS.timeout):**
- Text: "connection error", "network error", "fetch failed", etc.
- Regex: /\beconn(?:refused|reset|aborted)\b/i, /\benotfound\b/i, /\beai_again\b/i
**In `failover-error.ts` (TIMEOUT_HINT_RE):**
- Same patterns for non-assistant error paths
## Testing
Added test cases covering:
- "Connection error."
- "fetch failed"
- "network error: ECONNREFUSED"
- "ENOTFOUND" / "EAI_AGAIN" in message text
## Impact
- **Compatibility:** High - only expands retryable error detection
- **Behavior:** Connection failures now trigger automatic fallback
- **Risk:** Low - changes are additive and well-tested
* style: fix code formatting for test file
30ab9b2068