fix(macOS): paste Finder file paths

[kaluli123123]

Summary

• Read macOS Finder file URLs from the native general pasteboard before the terminal paste event is created.
• Decode file URLs to POSIX paths while preserving the existing text clipboard fallback.
• Keep the native adapter and Objective-C dependencies macOS-only.
• Migrate the implementation to the current crates/ui/terminal layout.

Root cause

The iced text clipboard path requests only an NSString representation. Finder publishes the selected file as public.file-url, so the existing paste handler cannot obtain the decoded POSIX path.

Verification on macOS

• Focused input regression test: passed.
• Clipboard adapter tests: 3 passed.
• cargo +nightly fmt -- --check: passed.
• cargo +1.96 lint: passed.
• cargo clippy --workspace --all-targets --all-features -- -D warnings: passed.
• cargo test --workspace --all-features: 530 passed, 2 ignored.
• cargo deny check: exited 0 with the existing yanked core2 0.4.0 and spin 0.9.8 warnings.
• cargo llvm-cov --workspace --all-features --fail-under-lines 80: exited 1 because workspace line coverage is 67.82%; changed clipboard.rs and input.rs line coverage is 98.18% and 81.83%.
• Native Finder smoke test passed with spaces and a Japanese wide-character filename; OTTY pasted the decoded absolute path without a file:// prefix.

PR #87 is merged. This branch is rebased onto the resulting main and now contains only the Finder paste changes. Local Linux and Windows target builds were not run on this macOS host.