fix(runtime-fallback): classify quota exhaustion as STOP not retryable

Remove quota exhaustion patterns from RETRYABLE_ERROR_PATTERNS:

- 'usage limit reached' patterns (lines 30, 32)

- 'insufficient credits' pattern (line 37)

- 'credit balance too low' pattern (line 38)

These errors indicate permanent quota exhaustion, not temporary

rate limits. They are already handled by classifyErrorType() which returns

'quota_exceeded', and isRetryableError() properly stops on these

unless there's an explicit auto-retry signal.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>