Remove unstable Java inlay hints from the macOS editor

[1lck]

Problem

The macOS Java editor renders parameter-name inlay hints as manually positioned AppKit overlays and reserves text space with attributed-string kerning. The overlays can drift vertically after layout changes, and repeated coordinate fixes have not made the optional feature reliable.

Decision

Remove the macOS inlay-hint presentation and refresh pipeline while preserving the shared Rust Core and Windows compatibility surfaces.

Acceptance criteria

• The macOS Java editor no longer renders parameter-name hint labels.
• The editor no longer inserts kerning to reserve space for those labels.
• Opening or editing Java files no longer scans project sources for fallback inlay hints.
• Code Vision, folding, blame, shared Rust contracts, and Windows behavior remain unchanged.
• macOS tests, service-boundary checks, and Rust Core bridge verification pass.

[1lck]

Implemented by #280, targeting the preview branch.

[1lck]

PR #280 已合入 preview，此 issue 按计划关闭。