Fix loader keyword args and centralize validation

[Teagan42]

What

• pass keyword arguments to load_media and its invocation of run so IMDb queue paths and other options remain aligned
• move require_positive into a shared mcp_plex.common.validation module and update callers to import it
• add regression tests covering the CLI IMDb queue plumbing and the stricter require_positive behaviour

Why

• prevent future regressions from positional argument mis-ordering in the loader
• ensure value validation is shared and type-safe across packages

Affects

• loader CLI orchestration
• shared validation utilities
• loader CLI and validation unit tests

Testing

• uv run ruff check .
• uv run pytest

Documentation

• not needed

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https://chatgpt.com/codex/tasks/task_e_68e36c699574832884007e8e56d9f919

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex/loader
__init__.py	388	18	95%	84–91, 165, 255–260, 621, 736–738, 740, 826–845, 1198
mcp_plex/loader/pipeline
__init__.py	16	7	56%	57–62, 68
channels.py	59	2	97%	20–21
enrichment.py	431	60	86%	248, 253, 284, 286, 293, 297, 376, 397, 417, 425–427, 434–437, 440–442, 450, 507, 563, 586, 590, 592, 618, 636, 648, 677, 683, 686–694, 720, 723–725, 742–744, 764–767, 771, 785–791, 813, 815, 818–820
ingestion.py	81	8	90%	66, 97–107, 128, 156, 178
orchestrator.py	85	5	94%	48, 112, 141, 164–165
persistence.py	125	9	93%	112, 154–155, 165, 170, 174–176, 214
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	2062	149	93%

Tests	Skipped	Failures	Errors	Time
130	0 💤	0 ❌	0 🔥	46.398s ⏱️