Render colored inline diffs for file-edit tool calls

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: corteza
 Title: AI Agent Runtime
-Version: 0.6.6.1
+Version: 0.6.6.2
 Authors@R: c(
     person("Troy", "Hernandez", role = c("aut", "cre"),
            email = "troy@cornball.ai",

NEWS.md

@@ -1,3 +1,30 @@
+# corteza 0.6.6.2
+
+## Inline diffs on file edits
+
+* `replace_in_file` and `write_file` now attach a unified-diff payload
+  to their MCP result. The CLI and `corteza::chat()` render it inline
+  in the tool-call output as `⎿ Added N, removed M` followed by one
+  row per kept line (`NNNN +|-| content` with red/green color) instead
+  of the prior `N lines in Xms` summary. The LLM-facing result text is
+  unchanged — the diff is for the human reading the terminal.
+* Tool labels renamed for clarity: `replace_in_file` → "Update",
+  `write_file` → "Write" (matches the inline-diff phrasing).
+* Diff generation shells out to the system `diff -u`. If `diff` isn't
+  on `PATH` the tool degrades to a one-line size summary rather than
+  failing. Diff payload is capped at 200 lines / 20000 chars with a
+  `[diff truncated: N more lines]` marker so big writes don't dump
+  thousands of lines into chat scrollback.
+* The `/diff` slash command's output is also ANSI-colored.
+
+## Console color policy is shared
+
+* `ansi_supported()` / `ansi_colors()` in the package are now the
+  single source of truth for both `corteza::chat()` and the
+  `~/bin/corteza` CLI. RStudio's R console (which is not a tty) is now
+  correctly detected as ANSI-capable, and `NO_COLOR` / `FORCE_COLOR`
+  overrides work in both surfaces.
+
 # corteza 0.6.6.1
 
 ## Interrupt key

R/cli-colors.R

@@ -12,6 +12,21 @@
 #' @return Single logical.
 #' @noRd
 ansi_supported <- function() {
+    # NO_COLOR / FORCE_COLOR are the conventional overrides; they win
+    # over auto-detection so users can force either side. RStudio's R
+    # console pane is not a tty (isatty(stdout()) is FALSE) but it
+    # does render ANSI escape sequences — without the RSTUDIO check,
+    # corteza::chat() would emit plain text in RStudio while the
+    # terminal CLI gets colored output.
+    if (nzchar(Sys.getenv("NO_COLOR"))) {
+        return(FALSE)
+    }
+    if (nzchar(Sys.getenv("FORCE_COLOR"))) {
+        return(TRUE)
+    }
+    if (identical(Sys.getenv("RSTUDIO"), "1")) {
+        return(TRUE)
+    }
     if (.Platform$OS.type == "windows") {
         return(any(nzchar(Sys.getenv(c("WT_SESSION", "ConEmuANSI",
                                        "TERM_PROGRAM")))))
@@ -46,3 +61,46 @@ ansi_colors <- function() {
          bright_magenta = "\033[95m", bright_cyan = "\033[96m")
 }
 
+#' Colorize a unified-diff string for terminal display.
+#'
+#' Matches `git diff` / `git --color=always`'s palette: green additions,
+#' red deletions, cyan hunk headers, bold file headers, dim metadata
+#' lines. The `+++ ` / `--- ` file-header check has to run before the
+#' bare `+` / `-` check or the file-header lines would be colored as
+#' add/delete rows.
+#'
+#' Returns `text` unchanged when the terminal doesn't support ANSI.
+#' @param text Character scalar, raw diff output.
+#' @param palette Optional palette from \code{ansi_colors()}; tests pass
+#'   a forced palette to assert escape sequences are emitted.
+#' @return Character scalar with ANSI escapes interleaved.
+#' @noRd
+colorize_diff <- function(text, palette = ansi_colors()) {
+    if (!is.character(text) || length(text) != 1L || !nzchar(text)) {
+        return(text)
+    }
+    if (!nzchar(palette$reset)) {
+        return(text)
+    }
+    lines <- strsplit(text, "\n", fixed = TRUE)[[1]]
+    paint <- function(ln) {
+        if (startsWith(ln, "diff --git ") || startsWith(ln, "index ") ||
+            startsWith(ln, "similarity ") || startsWith(ln, "rename ") ||
+            startsWith(ln, "new file") || startsWith(ln, "deleted file")) {
+            paste0(palette$dim, ln, palette$reset)
+        } else if (startsWith(ln, "+++ ") || startsWith(ln, "--- ")) {
+            paste0(palette$bold, ln, palette$reset)
+        } else if (startsWith(ln, "@@")) {
+            paste0(palette$cyan, ln, palette$reset)
+        } else if (startsWith(ln, "+")) {
+            paste0(palette$green, ln, palette$reset)
+        } else if (startsWith(ln, "-")) {
+            paste0(palette$red, ln, palette$reset)
+        } else {
+            ln
+        }
+    }
+    paste(vapply(lines, paint, character(1L), USE.NAMES = FALSE),
+          collapse = "\n")
+}
+

R/cli-ui.R

@@ -119,9 +119,9 @@ cli_tool_label <- function(tool_name, long = FALSE) {
                     run_r_script = "Run R Script",
                     read_file = "Read File",
                     "base::readLines" = "Read File",
-                    write_file = "Write File",
-                    "base::writeLines" = "Write File",
-                    replace_in_file = "Replace in File",
+                    write_file = "Write",
+                    "base::writeLines" = "Write",
+                    replace_in_file = "Update",
                     list_files = "List Files",
                     "base::list.files" = "List Files",
                     grep_files = "Grep Files",
@@ -144,7 +144,7 @@ cli_tool_label <- function(tool_name, long = FALSE) {
            run_r = "Run R code", run_r_script = "Run R script",
            read_file = "Read file", "base::readLines" = "Read file",
            write_file = "Write file", "base::writeLines" = "Write file",
-           replace_in_file = "Replace in file", list_files = "List files",
+           replace_in_file = "Update file", list_files = "List files",
            "base::list.files" = "List files", grep_files = "Search files",
            web_search = "Web search", fetch_url = "Fetch URL",
            git_status = "Git status", git_diff = "Git diff",