#1620 chore: Simplify native CLI install path handling

Summary

• Preserve native CLI setup behavior while separating install path resolution from process execution and orchestration.
• Keep existing public installer and setup APIs unchanged.

User Impact

• No user-visible behavior change.
• Install, uninstall, PATH setup, and package-owned CLI detection continue to use the same paths, comparisons, and commands.

Changes

• Move install path calculation, comparison, ownership checks, and environment reads into NativeCliInstallPathResolver.
• Keep current-process PATH writes in NativeCliInstaller, maintaining a clear read/write boundary.
• Move uninstall command construction into NativeCliCommandBuilder after path resolution becomes an independent dependency.
• Update production callers and existing tests to reference the extracted responsibilities directly without compatibility wrappers.
• Restore QuoteProcessArgument from internal to private visibility after all command construction becomes builder-internal; this is the only non-move production change.

Verification

• Unity compile: 0 errors, 0 warnings
• NativeCliInstallerTests: 32 passed
• Related detector, PATH setup, application service, and static guard fixtures: 51 passed
• No resolver-to-installer reverse references
• No IPC or protocol changes

Review Follow-up

• CodeRabbit and cubic identified a pre-existing raw PATH comparison that can leave a trailing-separator duplicate in the current-process PATH.
• The finding is recorded as R2-29 [Medium] for a separate Red-Green TDD fix so this PR retains its move-only review guarantee; CLI resolution and the persisted User PATH are unaffected.