fix(web): diff card review — TUI parity, path-header overlap, double-resolve

Bring the TUI diff footer onto the same terminator rule and distinct-path
count the Web DiffBlock uses (a trailing newline terminates its line; two
hunks in one file read as 1 file), so the two front ends' `+A -R · N file(s)`
footers agree. Reserve space in the diff path header for the floating copy
button so a long path no longer scrolls under it. Pass the tool's raw path to
the injected openFile (which already resolves against cwd) instead of resolving
twice. Rename the shared block-body CSS class to a card-neutral cardBody so a
terminal-spacing tweak cannot silently move the diff card. Add a same-file
two-hunk TUI unit test and an assembled built-boot assertion that the write
turn renders +1 -0 · 1 file end to end.

packages/client/ui-primitives/src/DiffBlock.module.css

@@ -46,10 +46,14 @@
   white-space: pre;
 }
 
-/* A file header: the path in the primary tone, set apart by weight. */
+/* A file header: the path in the primary tone, set apart by weight. The copy
+   button floats over this first row's top-right corner, so reserve space at the
+   line's end for it — a long path scrolls under the button otherwise, and the
+   button's hit area would eat clicks on the path's tail. */
 .path {
   color: var(--dsw-alias-label-primary);
   font-weight: 600;
+  padding-right: 56px;
 }
 
 /* A same-file second hunk's separator (a scattered edit), in the dim tone. */

packages/client/ui-primitives/src/DiffBlock.tsx

@@ -4,9 +4,10 @@
 // color), with a dim `└ +A -R · N file(s)` footer. The +/- block form mirrors
 // the TUI transcript's diff card (packages/ui/tui: diffLines) so a diff reads
 // the same across front ends: the removed side is the old text in full, the
-// added side the new text in full. Output never soft-wraps — an aligned source
-// line keeps its indentation and scrolls horizontally instead of folding.
-// Colors resolve through --dsw-* tokens; geometry mirrors CodeBlock.
+// added side the new text in full, both split on the same terminator rule, and
+// the footer counts distinct paths on both ends. Output never soft-wraps — an
+// aligned source line keeps its indentation and scrolls horizontally instead of
+// folding. Colors resolve through --dsw-* tokens; geometry mirrors CodeBlock.
 
 import { useCallback, useMemo, useState } from 'react'
 import clsx from 'clsx'
@@ -68,9 +69,8 @@ const ROW_CLASS: Record<DiffRow['kind'], string | undefined> = {
  * opens each new file; a same-file second hunk (a scattered edit) opens with a
  * `⋯` gap instead of repeating the path. Every old-side line counts toward
  * `removed` and every new-side line toward `added`. The file count is of
- * DISTINCT paths, which is the one deliberate divergence from the TUI diff card:
- * the TUI footer uses `diffs.length`, so two hunks in one file read there as
- * `2 files`, whereas this counts the one file they belong to.
+ * DISTINCT paths, matching the TUI diff card's footer, so two hunks in one file
+ * read as `1 file` on both front ends.
  * @param diffs - the hunks to render.
  * @returns the body rows, the +/- totals, and the distinct-file count.
  */