Add opt-in vendor exclusion to class-name collision inspection

[Copilot]

Class name collision inspection currently treats vendor-defined classes as equal collision candidates, which creates noise for application code. This change adds an opt-in mode to ignore collisions originating from the project’s vendor tree.

• Inspection configuration

  • Added ignoreVendorClasses boolean option to ClassNameCollisionInspection (default false).
  • Exposed in inspection UI via a checkbox: Ignore vendor classes.

• Collision filtering behavior

  • Collision lookup now excludes vendor classes only when the option is enabled.
  • Vendor detection is VFS-based and scoped to the project’s vendor directory (strict ancestry check), avoiding raw-path heuristics.

• Coverage updates

  • Added focused tests for:
    • vendor collision ignored when option is enabled
    • vendor collision still reported when option is disabled

• Inspection docs

  • Updated inspection help text to describe the new option and its effect.

@JvmField
var ignoreVendorClasses = false

override fun createOptionsPanel(): JComponent =
    SingleCheckboxOptionsPanel("Ignore vendor classes", this, "ignoreVendorClasses")

• Fixes [name collision] do not check vendor classes #85