feat(connectors): fix state & memory leak, test all plugins, enrich sinks

[spetz]

Connectors runtime lost state on restart - sink connectors resumed from offset 0 instead of their last committed position. The root cause was twofold: consumer group offset queries required membership (which new runtime instances lacked), and stale members from closed TCP connections blocked partition assignment to new members.

Consumer group offset resolution now supports direct queries without membership for ConsumerGroup consumers, since offsets are stored per group+partition, not per member. Stale member cleanup during join removes members whose client connections no longer exist, enabling proper partition rebalancing.

Runtime architecture refactored to fix memory leaks - replaced centralized status manager with DashMap-based SinkManager and SourceManager. Explicit channel cleanup on shutdown prevents dangling references.

State management uses MessagePack serialization for efficient binary persistence. PostgreSQL source fixed to actually return state from poll() and moved database I/O outside mutex to eliminate lock contention.

Additional changes:

• Replaced chrono with IggyTimestamp across SDK and connectors
• Added shared API types in sdk/src/api.rs for runtime HTTP API
• Sink connectors track state, enrich with Iggy metadata, retry transient errors with exponential backoff
• Comprehensive integration tests for all connector plugins

[codecov]

Codecov Report

❌ Patch coverage is 71.29630% with 124 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.35%. Comparing base (4052619) to head (576bf8f).

Files with missing lines	Patch %	Lines
core/connectors/runtime/src/source.rs	29.31%	33 Missing and 8 partials ⚠️
core/connectors/runtime/src/sink.rs	23.68%	24 Missing and 5 partials ⚠️
core/server/src/shard/system/consumer_groups.rs	32.35%	23 Missing ⚠️
core/connectors/sources/postgres_source/src/lib.rs	93.81%	4 Missing and 2 partials ⚠️
core/server/src/metadata/absorb.rs	66.66%	3 Missing and 1 partial ⚠️
core/common/src/utils/timestamp.rs	50.00%	3 Missing ⚠️
core/connectors/sdk/src/lib.rs	86.95%	2 Missing and 1 partial ⚠️
core/connectors/sdk/src/sink.rs	0.00%	3 Missing ⚠️
core/connectors/sdk/src/transforms/json/mod.rs	50.00%	3 Missing ⚠️
core/connectors/runtime/src/api/models.rs	0.00%	1 Missing and 1 partial ⚠️
... and 5 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2685      +/-   ##
==========================================
+ Coverage   69.52%   70.35%   +0.83%     
==========================================
  Files         568      568              
  Lines       55238    55505     +267     
  Branches    55238    55505     +267     
==========================================
+ Hits        38404    39052     +648     
+ Misses      14956    14537     -419     
- Partials     1878     1916      +38     

Flag	Coverage Δ
rust	70.35% <71.29%> (+0.83%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
core/connectors/runtime/src/api/mod.rs	50.68% <100.00%> (-1.32%)	⬇️
core/connectors/runtime/src/configs/connectors.rs	28.18% <ø> (ø)
...s/runtime/src/configs/connectors/local_provider.rs	55.24% <ø> (ø)
core/connectors/runtime/src/context.rs	88.09% <ø> (ø)
core/connectors/runtime/src/main.rs	80.59% <100.00%> (+1.73%)	⬆️
core/connectors/runtime/src/manager/sink.rs	63.63% <ø> (+5.45%)	⬆️
core/connectors/runtime/src/manager/source.rs	78.18% <ø> (+20.00%)	⬆️
core/connectors/runtime/src/stats.rs	75.00% <ø> (+22.50%)	⬆️
core/connectors/sdk/src/api.rs	100.00% <100.00%> (ø)
core/connectors/sdk/src/encoders/proto.rs	71.62% <100.00%> (ø)
... and 19 more

... and 18 files with indirect coverage changes

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