lint: two resolver divergences from Obsidian left open by #163

Follow-up to #163, whose main complaint (dot-prefixed directories walked as link candidates) shipped in v2.2.0. Two smaller divergences from the reporter's comment thread remain:

1. .md, .canvas, and .base are all stem-addressable (claude_obsidian/lint_engine.py, _EXTENSIONLESS_WIKILINK_SUFFIXES), so a .md landing note and a same-named .base report as ambiguous where Obsidian resolves deterministically.
2. <Name>.md.md resolution order differs from Obsidian.

Both need a documented Obsidian resolution order as the source of truth before changing the engine.