fix: Scope resolution treats .md files under resource dirs as fleet config

[TsekNet]

Problem

When an MR changes markdown files under fleet resource directories (e.g. policies/README.md, labels/README.md), scope resolution incorrectly treats them as fleet-relevant files:

• labels/README.md triggers IncludeGlobal = true
• policies/README.md, scripts/README.md, etc. match isFleetResource() and trigger team lookups

This causes fleet-plan to run a full diff against the live API for docs-only MRs, surfacing unrelated config changes (e.g. ABM/VPP field drift) that have nothing to do with the MR.

Root Cause

isFleetResource() only checks directory prefix, not file type. The labels/ check in ResolveScope similarly has no extension filter.

Fix

Exclude .md files from isFleetResource() and the labels/ global trigger.

[TsekNet]

Resolved via #29