fix(infra): single-read file_read (no double disk I/O for hash) + bail health poll on dead process

infrastructure/tools/filesystem/src/main/kotlin/com/correx/infrastructure/tools/filesystem/FileReadTool.kt

@@ -141,7 +141,10 @@ class FileReadTool(
     }
 
     private fun readFile(path: Path, startLine: Int?, endLine: Int?, request: ToolRequest): ToolResult = runCatching {
-        val lines = Files.readAllLines(path)
+        // Read the file once. Lines and the (whole-read) content hash both derive from these bytes,
+        // so a full read no longer hits the disk twice (readAllLines + readAllBytes for the hash).
+        val bytes = Files.readAllBytes(path)
+        val lines = bytes.inputStream().bufferedReader().readLines()
         val start = ((startLine ?: 1) - 1).coerceAtLeast(0)
         val end = (endLine ?: lines.size).coerceAtMost(lines.size)
         val selected = lines.subList(start, end)
@@ -166,7 +169,7 @@ class FileReadTool(
         // against what the agent actually saw. A partial or truncated view establishes no baseline —
         // the agent must read the relevant range before editing.
         val sawWholeFile = startLine == null && endLine == null && !lineCapped && !charCapped
-        val metadata = if (sawWholeFile) mapOf("contentHash" to sha256(path)) else emptyMap()
+        val metadata = if (sawWholeFile) mapOf("contentHash" to sha256(bytes)) else emptyMap()
         ToolResult.Success(
             invocationId = request.invocationId,
             output = content + note,
@@ -180,8 +183,8 @@ class FileReadTool(
         )
     }
 
-    private fun sha256(path: Path): String =
-        java.security.MessageDigest.getInstance("SHA-256").digest(Files.readAllBytes(path))
+    private fun sha256(bytes: ByteArray): String =
+        java.security.MessageDigest.getInstance("SHA-256").digest(bytes)
             .joinToString("") { "%02x".format(it) }
 
     private fun listDir(path: Path, request: ToolRequest): ToolResult = runCatching {