feat: add Plex ingestion batching helper

[Teagan42]

What

• add an async _ingest_plex helper that batches Plex movies and episodes onto the ingestion queue using _chunk_sequence
• emit per-batch logging with the stage logger and fall back gracefully when Plex stubs omit methods
• expand ingestion stage tests with fake Plex server fixtures to assert batching order and log output, and bump the project version to 0.26.64

Why

• support configurable Plex ingestion batching while exercising the new helper with deterministic tests

Affects

• loader ingestion stage batching and logging
• ingestion stage unit tests
• project version metadata

Testing

• uv run pytest
• uv run pytest tests/test_ingestion_stage.py

Documentation

• n/a

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https://chatgpt.com/codex/tasks/task_e_68e2af58e5688328991b0c3fc5a0cf0c

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex/loader
__init__.py	816	131	84%	192, 247, 249–251, 267, 353–358, 960–961, 1005, 1007, 1060–1061, 1072–1074, 1077, 1080–1081, 1083, 1105, 1115, 1126–1158, 1173, 1175, 1182–1196, 1199–1213, 1219, 1234–1265, 1270–1303, 1306–1310, 1315–1323, 1333, 1342, 1346–1348, 1467–1469, 1802
mcp_plex/loader/pipeline
channels.py	70	2	97%	19–20
ingestion.py	81	8	90%	67, 98–108, 129, 157, 179
mcp_plex/server
__init__.py	614	29	95%	43–44, 119–120, 148, 252, 256, 277–280, 297, 362, 365, 402, 420–421, 458, 1109, 1131–1137, 1173, 1191, 1196, 1214, 1338, 1375
__main__.py	4	4	0%	3–8
config.py	48	7	85%	50, 52–55, 65, 76
TOTAL	1843	181	90%

Tests	Skipped	Failures	Errors	Time
106	0 💤	0 ❌	0 🔥	48.843s ⏱️