docs: clarify user guidance and monitor setup

[nuxencs]

Why

User-facing documentation included retry mechanics and provider implementation details that do not help with setup or recovery. Monitor examples also used inconsistent config paths.

What changed

• Replace retry internals with recovery guidance that preserves skip, force, and rate-limit limitations.
• Clarify monitor setup with a writable downloadLocation and consistent explicit config-directory examples.
• Keep implementation-level retry details in maintainer docs and simplify Comix guidance.

Tests

• Verified repository-local Markdown links and anchors with a local checker.
• Verified mangarr download --help and mangarr monitor --help locally.
• CI's offline Lychee check passed: 73 successful links, 0 errors across 149 links.
• Lychee was unavailable locally, so no local Lychee run, live provider traffic, or real downloads were used.