fix: Critical code review fixes — race conditions, panic recovery, LTRIM/RTRIM

CRITICAL fixes:
- fileio.go: Add sync.Mutex to file handle table (race condition #2)
  allocHandle/getHandle/removeHandle thread-safe helpers
- goroutine.go: Add defer/recover to GoLaunch/GoLaunchBlock
  Goroutine panic no longer crashes entire process (#5)

HIGH fixes:
- strings.go: Implement proper LTrim (TrimLeft) and RTrim (TrimRight)
  Previously both aliased to AllTrim — silent semantic bug (#18)
- register.go: TRIM = RTrim (Harbour compatible)

From 53-issue senior code review.
Remaining: 47 issues (HIGH: 10, MEDIUM: 18, LOW: 16, CRITICAL: 3)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/.pdca-status.json

@@ -1,6 +1,6 @@
 {
   "version": "2.0",
-  "lastUpdated": "2026-03-31T02:56:59.267Z",
+  "lastUpdated": "2026-04-01T01:16:33.700Z",
   "activeFeatures": [
     "hbrt",
     "hbrtl",
@@ -33,9 +33,9 @@
       "documents": {},
       "timestamps": {
         "started": "2026-03-27T09:33:04.512Z",
-        "lastUpdated": "2026-03-31T01:15:54.989Z"
+        "lastUpdated": "2026-04-01T01:14:37.127Z"
       },
-      "lastFile": "/mnt/d/charles/five/hbrt/dynamic_syntax_test.go"
+      "lastFile": "/mnt/d/charles/five/hbrt/goroutine.go"
     },
     "hbrtl": {
       "phase": "do",
@@ -46,9 +46,9 @@
       "documents": {},
       "timestamps": {
         "started": "2026-03-27T11:15:10.675Z",
-        "lastUpdated": "2026-03-31T01:06:49.182Z"
+        "lastUpdated": "2026-04-01T01:16:33.700Z"
       },
-      "lastFile": "/mnt/d/charles/five/hbrtl/rawtty.go"
+      "lastFile": "/mnt/d/charles/five/hbrtl/register.go"
     },
     "tests": {
       "phase": "do",
@@ -280,7 +280,7 @@
   "session": {
     "startedAt": "2026-03-27T06:06:49.620Z",
     "onboardingCompleted": false,
-    "lastActivity": "2026-03-31T02:56:59.267Z"
+    "lastActivity": "2026-04-01T01:16:33.700Z"
   },
   "history": [
     {
@@ -5418,6 +5418,72 @@
       "feature": "mem",
       "phase": "do",
       "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T00:50:44.331Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T00:51:04.728Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T00:51:29.797Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T00:53:27.988Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T00:53:39.882Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T00:53:51.335Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T01:12:51.547Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T01:14:22.341Z",
+      "feature": "hbrt",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T01:14:37.127Z",
+      "feature": "hbrt",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T01:15:49.420Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
+    },
+    {
+      "timestamp": "2026-04-01T01:16:33.700Z",
+      "feature": "hbrtl",
+      "phase": "do",
+      "action": "updated"
     }
   ]
 }

docs/five-readability-en.md

@@ -115,7 +115,7 @@ if condition {
 ```prg
 LOCAL cCustomerName, nTotalBalance, dLastPurchase, lIsActive
 
-cCustomerName := "Charles Kwon"      // c = Character
+cCustomerName := "Charles KWON"       // c = Character
 nTotalBalance := 15000.50             // n = Numeric
 dLastPurchase := Date()               // d = Date
 lIsActive := .T.                      // l = Logical

hbrt/goroutine.go

@@ -8,6 +8,8 @@
 package hbrt
 
 import (
+	"fmt"
+	"os"
 	"sync"
 )
 
@@ -114,6 +116,11 @@ func (v Value) AsMutex() *HbMutex {
 // GoLaunch spawns a new goroutine that runs a function on a new Thread.
 func (vm *VM) GoLaunch(fn func(*Thread), args []Value) {
 	go func() {
+		defer func() {
+			if r := recover(); r != nil {
+				fmt.Fprintf(os.Stderr, "Five goroutine panic: %v\n", r)
+			}
+		}()
 		t := vm.NewThread()
 		for _, a := range args {
 			t.push(a)
@@ -126,6 +133,11 @@ func (vm *VM) GoLaunch(fn func(*Thread), args []Value) {
 // GoLaunchBlock spawns a goroutine that evaluates a code block.
 func (vm *VM) GoLaunchBlock(blk *HbBlock, args []Value) {
 	go func() {
+		defer func() {
+			if r := recover(); r != nil {
+				fmt.Fprintf(os.Stderr, "Five goroutine panic: %v\n", r)
+			}
+		}()
 		t := vm.NewThread()
 		for _, a := range args {
 			t.push(a)

hbrtl/fileio.go

@@ -13,14 +13,40 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 )
 
 // File handle table — maps Harbour handle (int) to Go *os.File
+// Protected by mutex for goroutine safety.
 var (
-	fileHandles = map[int]*os.File{}
+	fileHandles   = map[int]*os.File{}
-	nextHandle  = 10 // start from 10, avoid 0-2 (stdin/out/err)
+	nextHandle    = 10 // start from 10, avoid 0-2 (stdin/out/err)
+	fileHandlesMu sync.Mutex
 )
 
+// File handle helpers (thread-safe)
+func allocHandle(f *os.File) int {
+	fileHandlesMu.Lock()
+	defer fileHandlesMu.Unlock()
+	h := nextHandle
+	nextHandle++
+	fileHandles[h] = f
+	return h
+}
+
+func getHandle(h int) (*os.File, bool) {
+	fileHandlesMu.Lock()
+	defer fileHandlesMu.Unlock()
+	f, ok := fileHandles[h]
+	return f, ok
+}
+
+func removeHandle(h int) {
+	fileHandlesMu.Lock()
+	defer fileHandlesMu.Unlock()
+	delete(fileHandles, h)
+}
+
 // FOPEN(cFileName [, nMode]) → nHandle | -1
 // nMode: 0=read, 1=write, 2=readwrite
 func FOpen(t *hbrt.Thread) {
@@ -53,9 +79,7 @@ func FOpen(t *hbrt.Thread) {
 		return
 	}
 
-	h := nextHandle
+	h := allocHandle(f)
-	nextHandle++
-	fileHandles[h] = f
 	SetFError(0)
 	t.RetInt(int64(h))
 }
@@ -74,9 +98,7 @@ func FCreate(t *hbrt.Thread) {
 		return
 	}
 
-	h := nextHandle
+	h := allocHandle(f)
-	nextHandle++
-	fileHandles[h] = f
 	SetFError(0)
 	t.RetInt(int64(h))
 }
@@ -87,14 +109,14 @@ func FClose(t *hbrt.Thread) {
 	defer t.EndProc()
 
 	h := t.Local(1).AsInt()
-	f, ok := fileHandles[h]
+	f, ok := getHandle(h)
 	if !ok {
 		SetFError(6) // invalid handle
 		t.RetBool(false)
 		return
 	}
 	err := f.Close()
-	delete(fileHandles, h)
+	removeHandle(h)
 	SetFError(0)
 	t.RetBool(err == nil)
 }
@@ -107,7 +129,7 @@ func FRead(t *hbrt.Thread) {
 	h := t.Local(1).AsInt()
 	nBytes := t.Local(3).AsInt()
 
-	f, ok := fileHandles[h]
+	f, ok := getHandle(h)
 	if !ok {
 		SetFError(6)
 		t.RetInt(0)
@@ -139,7 +161,7 @@ func FWrite(t *hbrt.Thread) {
 	h := t.Local(1).AsInt()
 	data := t.Local(2).AsString()
 
-	f, ok := fileHandles[h]
+	f, ok := getHandle(h)
 	if !ok {
 		SetFError(6)
 		t.RetInt(0)
@@ -177,7 +199,7 @@ func FSeek(t *hbrt.Thread) {
 		origin = t.Local(3).AsInt()
 	}
 
-	f, ok := fileHandles[h]
+	f, ok := getHandle(h)
 	if !ok {
 		SetFError(6)
 		t.RetInt(0)

hbrtl/register.go

@@ -33,9 +33,9 @@ func RegisterRTL(vm *hbrt.VM) {
 		hbrt.Sym("UPPER", hbrt.FsPublic, Upper),
 		hbrt.Sym("LOWER", hbrt.FsPublic, Lower),
 		hbrt.Sym("ALLTRIM", hbrt.FsPublic, AllTrim),
-		hbrt.Sym("LTRIM", hbrt.FsPublic, AllTrim), // simplified alias
+		hbrt.Sym("LTRIM", hbrt.FsPublic, LTrim),
-		hbrt.Sym("RTRIM", hbrt.FsPublic, AllTrim), // simplified alias
+		hbrt.Sym("RTRIM", hbrt.FsPublic, RTrim),
-		hbrt.Sym("TRIM", hbrt.FsPublic, AllTrim),  // simplified alias
+		hbrt.Sym("TRIM", hbrt.FsPublic, RTrim),    // TRIM = RTRIM in Harbour
 		hbrt.Sym("SPACE", hbrt.FsPublic, Space),
 		hbrt.Sym("PADR", hbrt.FsPublic, PadR),
 		hbrt.Sym("PADL", hbrt.FsPublic, PadL),

hbrtl/strings.go

@@ -202,6 +202,32 @@ func AllTrim(t *hbrt.Thread) {
 	t.RetValue()
 }
 
+// LTrim trims leading spaces only. Harbour: LTRIM(cString) → cString
+func LTrim(t *hbrt.Thread) {
+	t.Frame(1, 0)
+	defer t.EndProc()
+	v := t.Local(1)
+	if v.IsString() {
+		t.PushString(strings.TrimLeft(v.AsString(), " "))
+	} else {
+		t.PushString("")
+	}
+	t.RetValue()
+}
+
+// RTrim trims trailing spaces only. Harbour: RTRIM(cString) / TRIM(cString)
+func RTrim(t *hbrt.Thread) {
+	t.Frame(1, 0)
+	defer t.EndProc()
+	v := t.Local(1)
+	if v.IsString() {
+		t.PushString(strings.TrimRight(v.AsString(), " "))
+	} else {
+		t.PushString("")
+	}
+	t.RetValue()
+}
+
 // Space returns a string of n spaces.
 // Harbour: Space(nCount) → cString
 func Space(t *hbrt.Thread) {