Adds automatic detection of git remote name when BASH_IT_REMOTE is not set,
fixing issues for users with non-standard remote names like 'me', 'upstream',
'fork', etc.

**Problem:**
Commands like `bash-it version`, `bash-it update`, and `bash-it doctor`
hard-coded the remote name as "origin", causing failures when users have
different remote naming conventions:
```
$ bash-it version
error: No such remote 'origin'
```

**Solution:**
Created `_bash-it-get-remote-name()` helper function that:
1. Returns BASH_IT_REMOTE if already set (preserves user override)
2. Auto-detects first available remote via `git remote | head -n 1`
3. Falls back to "origin" if no remotes found

Updated three functions to use auto-detection:
- `_bash-it-update-()` (lib/helpers.bash:254)
- `_bash-it-version()` (lib/helpers.bash:370)
- `_bash-it-doctor-summary()` (lib/helpers.bash:564)

**Benefits:**
- No configuration required for single-remote repos
- Works with any remote name (me, fork, upstream, etc.)
- Backward compatible: BASH_IT_REMOTE override still works
- Fallback to "origin" maintains existing behavior for edge cases

**Testing:**
- Verified with non-standard remote name 'me'
- Tested BASH_IT_REMOTE environment variable preservation
- Shellcheck passes with no warnings

Fixes Bash-it#2317

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>