Print home-relative install paths with ~ prefix

[dustinvannoy-db]

What

Cosmetic fix to installer success/log output. Three ok lines printed their destination with ${dir#$HOME/}, which strips the $HOME/ prefix — so global-scope installs logged bare, project-relative-looking strings:

✓ Agent skills (42, link) → .gemini/skills
✓ Agent skills (42, link) → .codeium/windsurf/skills
✓ Agent skills (42, link) → .gemini/antigravity/skills

Now:

✓ Agent skills (42, link) → ~/.gemini/skills
✓ Agent skills (42, link) → ~/.codeium/windsurf/skills
✓ Agent skills (42, link) → ~/.gemini/antigravity/skills

This matches the style already used by the uninstall plan output (install.sh:771).

Lines changed: 2072, 2135 (agent skills), 2492 (MLflow skills), plus the new TILDE constant at 85.

Note on why this isn't a literal ~

The obvious change is ${dir/#$HOME/~}, copying the uninstall-plan idiom. That form is not portable, and would have been a silent no-op for many users:

bash	${dir/#$HOME/~}
3.2.57 (macOS /bin/bash)	~/.gemini/skills ✅
5.2.37 (Homebrew, Linux)	/Users/me/.gemini/skills ❌

bash 5.2+ tilde-expands a bare ~ in the replacement text, turning it straight back into $HOME. Since the installer is commonly run via curl … | bash — picking up whichever bash is first on PATH — the literal form would leave the confusing output in place on Linux and for Homebrew-bash users. Escaping (\~) fails the other way, emitting a literal backslash on 3.2.

Holding the ~ in a variable (TILDE="~") suppresses tilde expansion and is correct on both. Verified on both versions.

The pre-existing ${p/#$HOME/~} lines in the uninstall path have the same latent issue, but they're out of scope here and left untouched.

Verification

• bash -n install.sh passes on both 3.2.57 and 5.2.37.
• Output format confirmed on both versions for .gemini/skills, .codeium/windsurf/skills, .gemini/antigravity/skills, and a non-$HOME project path (left absolute, as expected).
• End-to-end run with a sandboxed $HOME: log lines print ~/… while the real directories are still created at the same absolute paths.
• git diff touches only display strings plus the new constant — every mkdir -p "$dir", cp -R, and ln -s destination is unchanged.

Scope

Display-only. No changes to install destination logic, path construction, scope resolution (base_dir), antigravity/windsurf/gemini destination computation, or install_genie_code_skills.py.

This pull request and its description were written by Isaac.