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