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 `!`)

spec/alias/provider.go

@@ -0,0 +1,40 @@
+package alias
+
+import (
+	"sync"
+)
+
+type AliasEntry struct {
+	Name      string
+	Expansion string
+	Scope     string // "local" | "global"
+}
+
+type Provider interface {
+	ToolName() string
+	GetAliases(cwd string) []AliasEntry
+}
+
+var (
+	providers = make(map[string]Provider)
+	mu        sync.RWMutex
+)
+
+func Register(p Provider) {
+	mu.Lock()
+	defer mu.Unlock()
+	providers[p.ToolName()] = p
+}
+
+// Reset clears the registered providers map, restoring it to its initial empty state.
+func Reset() {
+	mu.Lock()
+	defer mu.Unlock()
+	providers = make(map[string]Provider)
+}
+
+func GetProvider(toolName string) Provider {
+	mu.RLock()
+	defer mu.RUnlock()
+	return providers[toolName]
+}