render: colourise diff details + widen card, no mid-line wrap

When details is a unified diff (the network-configs notify feeds
`git diff HEAD~1`), colour each line like a pager: additions green,
deletions red, hunk headers violet, file/meta headers dim. Non-diff
details (auto-log output) still render as a plain muted block.

Also widen the card 600->760px and switch the details <pre> from
pre-wrap/word-break to white-space:pre + overflow-x:auto so diff lines
scroll instead of wrapping into mush.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/send.py

@@ -168,6 +168,71 @@ def fetch_failing_log(
     return "\n".join(cleaned[-log_lines:]).strip()
 
 
+# --- diff rendering -------------------------------------------------------
+# When `details` is a unified diff (the network-configs notify feeds
+# `git diff HEAD~1`), colour each line the way a terminal pager would:
+# additions green, deletions red, hunk headers violet, file/meta headers dim.
+# Non-diff details (e.g. auto-log output) fall through to a single muted block.
+DIFF_ADD = OK_FG
+DIFF_DEL = ERROR_FG
+DIFF_HUNK = ACCENT_VIOLET
+DIFF_META = MUTED
+DIFF_CONTEXT = MUTED_STRONG
+
+_HUNK_RE = re.compile(r"^@@ -\d+(?:,\d+)? \+\d+(?:,\d+)? @@")
+# Lines that start with +/- but are file headers, not content changes.
+_META_PREFIXES = (
+    "diff --git ",
+    "index ",
+    "--- ",
+    "+++ ",
+    "new file mode ",
+    "deleted file mode ",
+    "old mode ",
+    "new mode ",
+    "rename ",
+    "similarity index ",
+    "copy ",
+    "Binary files ",
+)
+
+
+def _looks_like_diff(text: str) -> bool:
+    """True if `text` reads as a unified diff (has a git header or a hunk)."""
+    for ln in text.splitlines():
+        if ln.startswith("diff --git ") or _HUNK_RE.match(ln):
+            return True
+    return False
+
+
+def _diff_line_color(line: str) -> str:
+    if _HUNK_RE.match(line):
+        return DIFF_HUNK
+    if line.startswith(_META_PREFIXES):
+        return DIFF_META
+    if line.startswith("+"):
+        return DIFF_ADD
+    if line.startswith("-"):
+        return DIFF_DEL
+    return DIFF_CONTEXT
+
+
+def colorize_diff_html(details: str) -> str:
+    """Return inner HTML for the details <pre>: one coloured span per line."""
+    spans = [
+        f'<span style="color:{_diff_line_color(line)};">{escape(line)}</span>'
+        for line in details.split("\n")
+    ]
+    return "\n".join(spans)
+
+
+def details_inner_html(details: str) -> str:
+    """Colour-highlight diffs; otherwise escape as a plain muted block."""
+    if _looks_like_diff(details):
+        return colorize_diff_html(details)
+    return escape(details)
+
+
 def fact_rows(items: Iterable[tuple[str, str, str]]) -> tuple[str, str]:
     """Build the HTML <table> rows and plain-text lines for the fact list.
 
@@ -222,8 +287,8 @@ def render(
           <pre style="margin:0;padding:14px 16px;background:{CANVAS};
                       border:1px solid {BORDER};border-radius:8px;
                       color:{MUTED_STRONG};font-family:{FONT_MONO};
-                      font-size:12px;line-height:1.55;white-space:pre-wrap;
+                      font-size:12px;line-height:1.55;white-space:pre;
-                      word-break:break-word;overflow-x:auto;">{escape(details)}</pre>
+                      overflow-x:auto;">{details_inner_html(details)}</pre>
         </td></tr>
         """
 
@@ -240,8 +305,8 @@ def render(
   <table role="presentation" width="100%" cellpadding="0" cellspacing="0"
          border="0" style="background:{CANVAS};padding:32px 16px;">
     <tr><td align="center">
-      <table role="presentation" width="600" cellpadding="0" cellspacing="0"
+      <table role="presentation" width="760" cellpadding="0" cellspacing="0"
-             border="0" style="max-width:600px;width:100%;background:{SURFACE};
+             border="0" style="max-width:760px;width:100%;background:{SURFACE};
                                border:1px solid {BORDER};border-radius:12px;
                                overflow:hidden;">
         <tr><td style="padding:28px 32px 8px 32px;">