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. */