chore(tools): 2b 注入 proof 路径随仓库位置推导，缺失参数报错文案改正

proof 脚本原先硬编码 D 盘绝对路径，换机器就失效；仓库内已有同约定
（build-android.ps1 用 \ 推导），此处对齐。
text_check 的报错文案说「为空」，实际触发条件是 --units 缺失，改正。

tools/text_injection_proof.ps1

@@ -21,7 +21,9 @@
 # a stray injection would land in whatever window was foreground.
 
 $ErrorActionPreference = "Stop"
-$repo = "D:\working\projects\yuankong\remote"
+# Repo root derived from this script's location (tools/ is one level under the
+# repo root) so the proof runs on any clone, not just the author's D: drive.
+$repo = (Resolve-Path "$PSScriptRoot\..").Path
 $tmp  = "$env:TEMP\remote-text-proof"
 $base = "D:\working\environment"
 

viewer-core/examples/text_check.rs

@@ -33,7 +33,10 @@ fn arg(name: &str) -> Option<String> {
 
 fn parse_units(spec: &str) -> Result<Vec<u16>> {
     if spec.trim().is_empty() {
-        bail!("--units 为空：本轮要验证的是「有文本送出并被注入」，空输入没有验证价值");
+        bail!(
+            "--units 缺失或为空：本工具要验证的是「有文本送出并被注入」，\
+             空输入没有验证价值（空 Text 在产品路径上由 Session::send_text 拦掉）"
+        );
     }
     spec.split(',')
         .map(|s| s.trim())