refactor: remove legacy loader pipeline

[Teagan42]

What

• delete the legacy LoaderPipeline implementation from mcp_plex.loader
• refresh loader documentation and tests to reflect the staged pipeline API
• bump the package version to 0.26.75 and update dependency manifests

Why

• finish removing the legacy pipeline in favour of the staged loader orchestration helpers

Affects

• loader module API surface and project metadata

Testing

• uv run ruff check .
• uv run pytest

Documentation

• n/a

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https://chatgpt.com/codex/tasks/task_e_68e33d4c31a4832888ebaa61978ec561

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex/loader
__init__.py	462	20	96%	180–187, 236, 322–327, 736–737, 769, 782, 901–903, 967–984, 1326
mcp_plex/loader/pipeline
__init__.py	15	7	53%	57–62, 68
channels.py	73	2	97%	19–20
enrichment.py	430	43	90%	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, 744, 815, 818–820
ingestion.py	81	8	90%	67, 98–108, 129, 157, 179
orchestrator.py	85	5	94%	48, 112, 141, 164–165
persistence.py	124	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	2138	134	94%

Tests	Skipped	Failures	Errors	Time
128	0 💤	0 ❌	0 🔥	1m 0s ⏱️