test(chat): the margin guard must read every declaration, not the first

Review on #88: the guard used `.exec()` without /g on each rule body, so it inspected
only the FIRST `margin:` shorthand and the FIRST direct inline-margin longhand. A body
that declares a safe one and then an unsafe one would pass — and CSS applies the LAST
declaration, so the bar would sit against the window edge with a green test.

Correct, and reproduced before fixing. Injecting exactly the shape the reviewer named:

    #ctxBar { margin: 6px auto; margin: 0 8px 6px; }

the suite passed. That is the bug this test exists to catch, live, undetected.

Both scans are now matchAll over the whole body. The shorthand loop keeps the slot
parsing ([all] / [block inline] / [top inline bottom] / [top right bottom left]); the
longhand loop moved to strictEqual so it reads as "every one of these must be auto"
rather than "the first is not non-auto".

Same class of mistake as two others this session — an `indexOf` that found the wrong
`case 'listSessions'`, and an ordering assertion that passed when its subject was
absent. All three are a partial read standing in for a total one.

Re-verified, each by reverting the fix:
  - the review's case: safe shorthand then the bug
  - safe longhand then a bad longhand; safe shorthand then a bad longhand
  - the six original bypasses (reported bug, reviewBar, bgTasksBar, 4-slot asymmetric,
    direct margin-inline, shell column dropping margin-inline)
  - three controls still pass: `margin: 6px auto`, two auto shorthands in a row, and
    margin-inline: auto beside margin-block

34 suites green.

Author: ndemianc

extensions/levelcode-ai/test/webviewCss.test.js

@@ -753,18 +753,22 @@ test('SHELL COLUMN: no member re-declares an inline margin, which would un-centr
 			// A shorthand is only a problem when its INLINE slot is not auto. `margin: 8px auto`
 			// re-states the centring and is fine; `margin: 0 8px 6px` destroys it. Slots are
 			// [all] / [block inline] / [top inline bottom] / [top right bottom left].
-			const sh = /(?:^|;)\s*margin\s*:\s*([^;}]+)/.exec(body);
-			if (sh) {
+			//
+			// EVERY declaration, not the first: a single .exec() would read `margin: 6px auto`
+			// and stop, never reaching a `margin: 0 8px 6px` later in the same body — and CSS
+			// applies the LAST one, so the guard would pass while the bar sat against the edge.
+			for (const sh of body.matchAll(/(?:^|;)\s*margin\s*:\s*([^;}]+)/g)) {
 				const p = sh[1].trim().split(/\s+/);
 				const inline = p.length === 1 ? [p[0]] : p.length === 4 ? [p[1], p[3]] : [p[1]];
 				assert.ok(inline.every((v) => v === 'auto'),
 					id + ' has `margin: ' + sh[1].trim() + '` — its inline slot is not auto, so it '
 					+ 'resets margin-inline and pins the bar to one edge. Use margin-block; the width '
 					+ 'calc already insets by --shell-x.');
 			}
-			const direct = /margin-(?:left|right|inline(?:-start|-end)?)\s*:\s*([^;}]+)/.exec(body);
-			assert.ok(!direct || direct[1].trim() === 'auto',
-				id + ' sets an inline margin directly, which beats the shell column\'s auto');
+			for (const d of body.matchAll(/margin-(?:left|right|inline(?:-start|-end)?)\s*:\s*([^;}]+)/g)) {
+				assert.strictEqual(d[1].trim(), 'auto',
+					id + ' sets an inline margin directly, which beats the shell column\'s auto');
+			}
 		}
 	}
 });