chore(skills): tea-comment @filepath support and docs update

tea-comment now accepts @/path/to/file.md syntax to read comment body
from a file, avoiding $() subshells that break permission matching.
Updated pr-review skill and tea-cli rules with the new pattern.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tooling/tea-comment

@@ -1,15 +1,29 @@
 #!/usr/bin/env bash
 # Post a comment to a Gitea PR or issue.
 # Usage: tea-comment <number> "comment body"
+#        tea-comment <number> @/path/to/file.md
 set -euo pipefail
 
 if [[ $# -lt 2 ]]; then
-    echo "Usage: tea-comment <number> <comment>" >&2
+    echo "Usage: tea-comment <number> <comment|@filepath>" >&2
     exit 1
 fi
 
 NUMBER="$1"
-BODY="$2"
+INPUT="$2"
+
+# If the body starts with @, read from file
+if [[ "$INPUT" == @* ]]; then
+    FILEPATH="${INPUT#@}"
+    if [[ ! -f "$FILEPATH" ]]; then
+        echo "Error: file not found: $FILEPATH" >&2
+        exit 1
+    fi
+    BODY=$(cat "$FILEPATH")
+else
+    BODY="$INPUT"
+fi
+
 HASH=$(echo -n "$BODY" | md5sum | cut -c1-8)
 TMPFILE="/tmp/tea-comment-${NUMBER}-${HASH}.md"
 trap 'rm -f "$TMPFILE"' EXIT