These files had silent `except Exception: pass` blocks but no module
logger. Added `import logging` + `logger = logging.getLogger(__name__)`
at the top of each, then replaced the silent excepts with
`logger.debug(...)`.
- core/replaygain.py — 4 sites (id3 txxx + vorbis + mp4 atom reads)
- core/wishlist/presence.py — 3 sites (wishlist row parsing + queries)
- core/runtime_state.py — 1 site (activity toast emit)
- core/automation/signals.py — 1 site (collect known signals)
- core/download_engine/rate_limit.py — 1 site (plugin rate_limit_policy)
- api/system.py — 1 site (hydrabase status probe)
- api/search.py — 1 site (hydrabase search)
Refs #369
`core/download_engine/rate_limit.py` introduces a per-source
policy declaration: download_concurrency + download_delay_seconds.
Plugins declare via `RATE_LIMIT_POLICY` class attribute or a
`rate_limit_policy()` method.
Engine applies the declared policy to engine.worker at
register_plugin time — set_concurrency + set_delay get pushed
in automatically. Plugins without a declaration get the
conservative default (1 / 0). The set_engine callback fires
AFTER policy registration so config-driven sources (YouTube
reads user-tunable youtube.download_delay) can override.
Plan doc updated to reflect Phase D skip (search code is 90%
source-specific, not 60% — lifting it would be lossy or
bloated).
Pure additive — no plugin migrated yet. 8 tests pin the
resolution priority + engine wire-up + override semantics.
Suite still green (327 download tests).
