Scaffold all 7 hook events and eliminate type casting

- Add missing hook handlers: Stop, SubagentStop, PreCompact
- Replace all string type casting with proper JSON unmarshaling
- Change ToolUseRequest.Parameters from map[string]interface{} to json.RawMessage
- Update helper methods to use json.Unmarshal directly to typed structs
- Replace speech notifications with simple logging notifications
- Update documentation to reflect all hook events and remove speech references
- Add comprehensive CLAUDE.md with architecture overview and development guidance

All hooks now use type-safe JSON handling without .(string) assertions.
Complete coverage of Claude Code events: PreToolUse, PostToolUse,
UserPromptSubmit, Notification, Stop, SubagentStop, PreCompact.

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

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

internal/handlers/precompact.go

@@ -0,0 +1,69 @@
+package handlers
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/imjasonh/hooks/internal/hooks"
+)
+
+func init() {
+	hooks.RegisterHook(hooks.EventPreCompact, "*", HandlePreCompact)
+}
+
+// HandlePreCompact is triggered before Claude Code runs a compact operation to
+// reduce context window size. This can happen manually via /compact command
+// or automatically when the context window fills up.
+//
+// The matcher indicates the compaction trigger:
+// - "manual": User ran /compact command
+// - "auto": Automatic compaction due to context window limit
+//
+// Common use cases:
+// - Save conversation state before compaction
+// - Warn user about potential data loss
+// - Export important context to external files
+// - Create conversation backups
+// - Log compaction events for analysis
+func HandlePreCompact(ctx context.Context, input hooks.HookInput) (hooks.HookOutput, error) {
+	// Determine compaction type from the tool name/matcher
+	compactionType := "unknown"
+	if input.Tool == "manual" || input.ToolName == "manual" {
+		compactionType = "manual"
+	} else if input.Tool == "auto" || input.ToolName == "auto" {
+		compactionType = "auto"
+	}
+
+	slog.Info("pre-compaction hook triggered",
+		"session_id", input.SessionID,
+		"compaction_type", compactionType,
+		"cwd", input.CWD,
+		"transcript_path", input.TranscriptPath,
+		"timestamp", time.Now().Unix())
+
+	// Add context warning for the user
+	var warningContext string
+	if compactionType == "manual" {
+		warningContext = "Manual compaction requested - some conversation history will be summarized"
+	} else if compactionType == "auto" {
+		warningContext = "Automatic compaction triggered - context window limit reached"
+	} else {
+		warningContext = "Context compaction about to occur"
+	}
+
+	// TODO: Future enhancements could include:
+	// - Export full conversation before compaction
+	// - Save important code snippets or commands
+	// - Create conversation timeline backup
+	// - Allow user to specify what to preserve
+	// - Integration with external note-taking systems
+	// - Automatic git commit of current work
+	// - Context importance scoring and preservation
+
+	return hooks.HookOutput{
+		Decision:          "approve",
+		AdditionalContext: fmt.Sprintf("🔄 %s", warningContext),
+	}, nil
+}