fix(watcher): bound WatchedField change queue to prevent unbounded memory growth

[zeevdr]

Summary

• Closes Bound WatchedField change queue to prevent memory growth #100
• Add max_queue_size parameter (default 1024) to WatchedField and AsyncWatchedField
• Drop-oldest strategy: when the queue is full, the oldest entry is evicted and dropped_changes is incremented
• Log a WARNING on each drop (path, max size, running total)
• ConfigWatcher.field() and AsyncConfigWatcher.field() accept and forward max_queue_size
• Matches the TypeScript SDK's queue overflow semantics (DEFAULT_QUEUE_SIZE = 1024, drop-oldest)

Test plan

• dropped_changes starts at 0 and increments once per overflow
• Queue never exceeds max_queue_size entries
• Oldest entries are evicted (newest N survive)
• Warning logged with field path on each drop
• max_queue_size constructor arg sets the bound; default is 1024
• changes() / async for iterator yields only surviving entries after overflow
• Existing watcher tests pass unchanged

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 94.00000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
sdk/src/opendecree/async_watcher.py	92.00%	2 Missing ⚠️
sdk/src/opendecree/watcher.py	96.00%	1 Missing ⚠️

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