refactor: extract shared log-tracker factory to eliminate boilerplate duplication

[christso]

Problem

Four *-log-tracker.ts files each copy-paste ~70 lines of identical global store + subscriber logic:

• claude-log-tracker.ts
• codex-log-tracker.ts
• copilot-cli-log-tracker.ts
• copilot-sdk-log-tracker.ts

Each file implements the same pattern:

• Symbol.for() global store keys
• getLogStore() / getSubscriberStore() helpers
• notifySubscribers() with identical error swallowing
• recordXxxLogEntry() / consumeXxxLogEntries() / subscribeToXxxLogEntries()

Total: ~280 lines of duplicated boilerplate.

Proposal

Create a generic createLogTracker<T>(namespace: string) factory in a shared log-tracker-factory.ts that returns typed { record, consume, subscribe } functions. Each provider tracker becomes a one-liner.

Acceptance criteria

• Single shared factory function (~40 lines)
• All 4 trackers refactored to use it
• Existing public API (consumeXxxLogEntries, subscribeToXxxLogEntries) unchanged
• All tests pass