fix: correct zip root path and add idempotent build.prop append

- Fix ZIPROOT path from 3 to 4 levels up (../../../../)

- Add path validation before install

- Replace simple cat append with key-based dedup for build.prop (skips existing keys to prevent duplication on re-flash)

- Update AGENTS.md and README.md to reflect the changes

AGENTS.md

@@ -34,7 +34,7 @@ zip root
 
 ### Install flow (update-binary)
 
-1. Locate zip root: `dirname $0` → up 3 levels (`../../..`)
+1. Locate zip root: `dirname $0` → up 4 levels (`../../../../`)
 2. Mount `/system` and `/vendor`
 3. **Append** `system/build.prop` → `/system/build.prop` (backup first to `.bak`)
 4. Copy `goodix_ts.idc` → `/system/usr/idc/`
@@ -43,11 +43,23 @@ zip root
 
 ### Critical constraint: build.prop is APPENDED, never replaced
 
-`update-binary` line ~72: `cat "$BUILDPROP_SRC" >> /system/build.prop`
+`update-binary` now uses **key-based dedup**: each line is appended only if its
+key (`key=` before `=`) does not already exist in the target.
 
-The `>>` is intentional. Using `>` or `package_extract_dir` would clobber the
-device's existing properties. Re-flashing duplicates entries — warn the user or
-add idempotency if this becomes a problem.
+```sh
+# 去重追加：逐 key 检查，仅追加不存在的条目
+while IFS= read -r line || [ -n "$line" ]; do
+  case "$line" in
+    ''|'#'*) continue;;
+  esac
+  key="${line%%=*}"
+  if ! grep -q "^${key}=" /system/build.prop 2>/dev/null; then
+    echo "$line" >> /system/build.prop
+  fi
+done < "$BUILDPROP_SRC"
+```
+
+Re-flashing is now safe — entries are never duplicated.
 
 ## Key Files
 

META-INF/com/google/android/update-binary

@@ -33,7 +33,13 @@ abort() {
 # The script lives at:  META-INF/com/google/android/update-binary
 # Zip root is 3 levels up from the script's directory.
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
-ZIPROOT=$(cd "$SCRIPT_DIR/../../.." && pwd)
+# 脚本位于 META-INF/com/google/android/update-binary，向上4级到 zip 根
+ZIPROOT=$(cd "$SCRIPT_DIR/../../../../" && pwd)
+
+# 验证路径正确
+if [ ! -f "$ZIPROOT/system/build.prop" ]; then
+  abort "Cannot locate zip root (system/build.prop not found)."
+fi
 
 ui_print "========================================"
 ui_print "  CB-C6s-STU-GSI-Fixes"
@@ -68,8 +74,16 @@ fi
 cp /system/build.prop /system/build.prop.bak 2>/dev/null
 chmod 644 /system/build.prop.bak 2>/dev/null
 
-# APPEND — 使用 >> 追加而非覆盖
-cat "$BUILDPROP_SRC" >> /system/build.prop
+# 去重追加：逐 key 检查，仅追加不存在的条目
+while IFS= read -r line || [ -n "$line" ]; do
+  case "$line" in
+    ''|'#'*) continue;;
+  esac
+  key="${line%%=*}"
+  if ! grep -q "^${key}=" /system/build.prop 2>/dev/null; then
+    echo "$line" >> /system/build.prop
+  fi
+done < "$BUILDPROP_SRC"
 chmod 644 /system/build.prop
 
 ui_print "build.prop: entries appended. Backup at build.prop.bak"

README.md

@@ -76,9 +76,10 @@ During flash, TWRP will show:
 
 ## Notes
 
-- The `build.prop` entries are **appended, not replaced**. Re-flashing
-  the zip multiple times will duplicate the entries — restore from
-  `/system/build.prop.bak` if needed, or inspect the file first.
+- The `build.prop` entries are **appended with dedup** — each property key
+  (`key=value`) is only added if the key does not already exist in
+  `/system/build.prop`. Re-flashing the zip multiple times is safe and
+  will **not** duplicate entries.
 - The `sensor_config.xml` covers four camera sensor combinations:
   rear (`hi846`, `gc8034_rear`) and front (`hi846_front`, `gc8034`),
   each with OTP EEPROM tuning parameters.