feat(ssa): Agent channel UX optimization (Solution B) + Plan-and-Execute architecture design

SSA Agent channel improvements (12 code files, +931/-203 lines):
- Solution B: left/right separation of concerns (gaze guiding + state mutex + time-travel)
- JWT token refresh mechanism (ensureFreshToken) to fix HTTP 401 during pipeline
- Code truncation fix: LLM maxTokens 4000->8000 + CSS max-height 60vh
- Retry streaming code generation with generateCodeStream()
- R Docker structured errors: 20+ pattern matching + format_agent_error + line extraction
- Prompt iron rules: strict output format in CoderAgent System Prompt
- parseCode robustness: XML/Markdown/inference 3-tier matching + length validation
- consoleOutput type defense: handle both array and scalar from R Docker unboxedJSON
- Agent progress bar sync: derive phase from agentExecution.status
- Export report / view code buttons restored for Agent mode
- ExecutingProgress component: real-time timer + dynamic tips + step pulse animation

Architecture design (3 review reports):
- Plan-and-Execute step-by-step execution architecture approved
- Code accumulation strategy (R Docker stays stateless)
- 5 engineering guardrails: XML tags, AST pre-check, defensive prompts, high-fidelity schema, error classification circuit breaker

Docs: update SSA module status v4.1, system status v6.7, deployment changelist
Made-with: Cursor

r-statistics-service/utils/error_codes.R

@@ -67,7 +67,25 @@ ERROR_CODES <- list(
 R_ERROR_MAPPING <- list(
   "system is computationally singular" = "E005_SINGULAR_MATRIX",
   "did not converge" = "E006_CONVERGENCE_FAILED",
-  "constant" = "E007_VARIANCE_ZERO"
+  "constant" = "E007_VARIANCE_ZERO",
+  "object '.*' not found" = "E001_COLUMN_NOT_FOUND",
+  "undefined columns" = "E001_COLUMN_NOT_FOUND",
+  "subscript out of bounds" = "E100_INTERNAL_ERROR",
+  "cannot coerce" = "E002_TYPE_MISMATCH",
+  "non-numeric argument" = "E002_TYPE_MISMATCH",
+  "not meaningful for factors" = "E002_TYPE_MISMATCH",
+  "missing value where TRUE/FALSE needed" = "E100_INTERNAL_ERROR",
+  "replacement has" = "E100_INTERNAL_ERROR",
+  "could not find function" = "E101_PACKAGE_MISSING",
+  "there is no package called" = "E101_PACKAGE_MISSING",
+  "cannot open the connection" = "E100_INTERNAL_ERROR",
+  "singular gradient" = "E005_SINGULAR_MATRIX",
+  "rank deficien" = "E005_SINGULAR_MATRIX",
+  "contrasts can be applied only to factors" = "E002_TYPE_MISMATCH",
+  "need at least 2 observations" = "E004_SAMPLE_TOO_SMALL",
+  "not enough observations" = "E004_SAMPLE_TOO_SMALL",
+  "sample size must be" = "E004_SAMPLE_TOO_SMALL",
+  "groups with fewer than" = "E004_SAMPLE_TOO_SMALL"
 )
 
 # 构造错误响应（含用户友好提示）
@@ -86,6 +104,64 @@ make_error <- function(error_def, ...) {
   ))
 }
 
+#' Agent 通道专用：结构化错误格式
+#' 提取行号、错误分类、修复建议，方便 LLM 理解并修复
+format_agent_error <- function(e, code, warnings = list(), messages = character(0)) {
+  raw_msg <- conditionMessage(e)
+  
+  error_line <- NULL
+  line_match <- regmatches(raw_msg, regexpr("(line \\d+|at \\d+:\\d+|:( *)\\d+)", raw_msg))
+  if (length(line_match) > 0 && nchar(line_match[1]) > 0) {
+    nums <- regmatches(line_match[1], gregexpr("\\d+", line_match[1]))[[1]]
+    error_line <- as.integer(nums[1])
+  }
+  
+  error_context <- NULL
+  if (!is.null(error_line) && !is.null(code)) {
+    code_lines <- strsplit(code, "\n")[[1]]
+    start <- max(1, error_line - 3)
+    end <- min(length(code_lines), error_line + 3)
+    context_lines <- paste0(
+      ifelse(start:end == error_line, ">>> ", "    "),
+      sprintf("%3d| ", start:end),
+      code_lines[start:end]
+    )
+    error_context <- paste(context_lines, collapse = "\n")
+  }
+  
+  error_code <- "E_EXEC"
+  error_type <- "runtime"
+  user_hint <- raw_msg
+  
+  for (pattern in names(R_ERROR_MAPPING)) {
+    if (grepl(pattern, raw_msg, ignore.case = TRUE)) {
+      key <- R_ERROR_MAPPING[[pattern]]
+      info <- ERROR_CODES[[key]]
+      error_code <- info$code
+      error_type <- info$type
+      user_hint <- paste0(info$user_hint, " | ", raw_msg)
+      break
+    }
+  }
+  
+  friendly_msg <- paste0(
+    "[", error_code, "] ", raw_msg,
+    if (!is.null(error_line)) paste0(" (约第 ", error_line, " 行)") else "",
+    if (length(warnings) > 0) paste0("\n[Warnings] ", paste(utils::head(warnings, 5), collapse = "; ")) else ""
+  )
+  
+  list(
+    message = friendly_msg,
+    raw_error = raw_msg,
+    error_code = error_code,
+    error_type = error_type,
+    error_line = error_line,
+    error_context = error_context,
+    user_hint = user_hint,
+    warnings = if (length(warnings) > 0) warnings else NULL
+  )
+}
+
 # 尝试将 R 原始错误映射为友好错误码
 map_r_error <- function(raw_error_msg) {
   for (pattern in names(R_ERROR_MAPPING)) {