fix: ensure loader stages enqueue with nowait fallback

[Teagan42]

What

• add a shared enqueue_nowait helper that prefers non-blocking queue inserts and falls back to awaiting when full
• update ingestion, enrichment, and persistence stages to emit batches and sentinels via the helper and adjust sample instrumentation
• bump the project version to 1.0.15 and refresh the uv lock file

Why

• ensure loader stages push to their queues with put_nowait while still honoring backpressure semantics

Affects

• loader pipeline stages and associated enrichment test helpers

Testing

• uv run ruff check .
• uv run pytest

Documentation

• not required

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https://chatgpt.com/codex/tasks/task_e_68e46a6311d083288a79997347d750e3

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex/loader
__init__.py	386	18	95%	80–87, 161, 251–256, 633, 748–750, 752, 838–857, 1222
mcp_plex/loader/pipeline
__init__.py	16	7	56%	57–62, 68
enrichment.py	438	60	86%	245, 250, 281, 283, 290, 294, 398, 419, 439, 447–449, 456–459, 462–464, 472, 535, 591, 614, 618, 620, 650, 668, 680, 709, 715, 718–726, 752, 755–757, 774–776, 796–799, 803, 817–823, 845, 847, 850–852
ingestion.py	155	13	92%	80, 129–149, 187, 224, 240, 333, 339, 359
orchestrator.py	92	5	95%	48, 126, 155, 178–179
persistence.py	129	9	93%	113, 155–156, 166, 177, 181–183, 236
mcp_plex/server
__init__.py	645	32	95%	52–53, 133–134, 162, 231, 237–238, 300, 304, 325–328, 345, 410, 413, 450, 468–469, 506, 1157, 1179–1185, 1221, 1239, 1244, 1262, 1386, 1423
__main__.py	4	4	0%	3–8
config.py	48	7	85%	50, 52–55, 65, 76
TOTAL	2208	155	93%

Tests	Skipped	Failures	Errors	Time
142	0 💤	0 ❌	0 🔥	1m 24s ⏱️