feat(spec): support tool aliases (#107)

closes #57

IRIS now automatically read and suggest internal configuration aliases
for Git (`.gitconfig`, `.git/config`) and Cargo (`.cargo/config.toml`)

- Added the `Provider` interface and extended registry for CLI tools
that define aliases
- Git: parse aliases via `git config --show-scope`, supporting raw
tab/space separation and scope differentiation
- Cargo: traverse the directory tree upwards to root to read the
`.cargo/config.toml` configuration
- 0ms hot-path caching: key caching is calculated entirely via `os.Stat`
mtime (no subprocess spawn) combined with a 2-second TTL window to
ensure 0ms latency when typing
- Lookup integration: display alias suggestions at the subcommand level
and automatically expand aliases as the user enters further arguments
(ignore shell pipeline commands starting with `!`)

root/suggestions.go

@@ -25,7 +25,10 @@ func MergeResults(query string, mode string) []spec.Suggestion {
 	// add suggestion helper to deduplicate
 	addSuggestion := func(s spec.Suggestion) {
 		normalizedCmd := strings.TrimSpace(s.Cmd)
-		if normalizedCmd == "" || normalizedCmd == normalizedQuery {
+		if normalizedCmd == "" {
+			return
+		}
+		if s.Source != "alias" && normalizedCmd == normalizedQuery {
 			return
 		}
 		if s.Source == "" {