feat: tighten cache payload typing and validation

[Teagan42]

Summary

• add reusable JSONValue aliases for shared JSON payload structures and expose them from the common package
• refactor MediaCache, server helpers, and loader cache integrations to consume typed payload dictionaries and update validation/tests for stricter Plex tag coercion
• document the new typing expectations and bump the project version metadata

Testing

• uv run ruff check .
• uv run pytest

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https://chatgpt.com/codex/tasks/task_e_68e4952b6f7c83289f5605ddd75a099f

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex/common
validation.py	28	2	93%	37–38
mcp_plex/loader
__init__.py	407	18	96%	85–92, 166, 256–261, 663, 778–780, 782, 868–887, 1252
imdb_cache.py	43	2	95%	59, 63
mcp_plex/loader/pipeline
channels.py	64	2	97%	134–135
enrichment.py	516	75	85%	237, 259–265, 318, 323, 354, 356, 363, 367, 471, 492, 512, 520–522, 525–527, 530–532, 540–545, 553, 607–608, 632, 692–693, 709, 738, 745, 747, 751, 803, 821, 833, 862, 868, 871–879, 905, 908–910, 927–929, 949–952, 956, 970–976, 998, 1000, 1003–1005
ingestion.py	155	13	92%	81, 130–150, 185, 222, 238, 331, 337, 357
orchestrator.py	95	5	95%	63, 141, 170, 193–194
persistence.py	130	9	93%	122, 164–165, 175, 186, 190–192, 245
mcp_plex/server
__init__.py	652	32	95%	53–54, 134–135, 163, 213, 239, 245–246, 315, 336–339, 356, 421, 424, 461, 479–480, 517, 1191, 1213–1219, 1255, 1273, 1278, 1296, 1420, 1457
__main__.py	4	4	0%	3–8
config.py	48	7	85%	50, 52–55, 65, 76
TOTAL	2341	169	93%

Tests	Skipped	Failures	Errors	Time
149	0 💤	0 ❌	0 🔥	1m 8s ⏱️