fix(live): land valid TSX through wrap → preview → accept → carbonize

Closes #114.

Three orthogonal bugs that surfaced together when live mode picked an
element inside a Vite React/TSX component with sibling branches:

1. JSX wrapper insertion produced invalid TSX
   - Replacing a single picked JSX child with [comment, <div>, comment]
     yields three adjacent siblings, which oxc rejects with "Adjacent
     JSX elements must be wrapped in an enclosing tag."
   - A Fragment `<></>` solves the adjacency case but breaks
     `cloneElement`-using parents (Radix `asChild`, Headless UI, etc.)
     with "Invalid prop supplied to React.Fragment."
   - Fix: keep the wrapper `<div data-impeccable-variants="ID">` as the
     single JSX-slot child and tuck both marker comments INSIDE it.
     accept/discard now expands its replacement range to include the
     wrapper's `<div>` open/close lines via div-depth tracking.

2. carbonize produced nested template literals in TSX `<style>`
   - extractCss captured `{` / `` `} `` lines from the agent's existing
     `<style>{`…`}</style>` template, then handleAccept re-wrapped with
     another pair, producing `<style>{`{`@scope…`}`}</style>` which oxc
     rejects with "Expected `}` but found `@`".
   - Fix: extractCss now strips a leading `{` and trailing `` `} ``
     wherever they appear in the captured content (own line OR attached
     to the first/last CSS line), so re-wrapping always yields exactly
     one `{` ` … ` `}` pair.

3. Ambiguous source matching for repeated JSX branches
   - `findElement` returned the first substring match. Multiple
     `<aside className="card">` siblings all matched the same query, so
     wrap silently landed on the first regardless of which one the user
     picked.
   - Fix: live-wrap accepts `--text TEXT` (the picked element's
     textContent), collects ALL candidates via `findAllElements`, and
     narrows by a tag-stripped, JSX-expression-stripped substring match.
     Returns `element_ambiguous + candidates[]` when multiple branches
     match equally; falls back to first-match when source uses dynamic
     content (`<h1>{title}</h1>`) so existing flows aren't broken.
   - The fake e2e agent now forwards `event.element.textContent` to
     wrap, and live.md tells the agent to do the same.

Test coverage:
- New `vite8-react-tsx-repeated-aside` e2e fixture: three identical
  `<aside>` branches, picks the second card's <h1>, runs the full
  wrap → Go → cycle → accept → carbonize cycle on a real Vite + TSX
  dev server, asserts that Hero One and Hero Three survive untouched
  (proving wrap landed on the correct branch).
- Six new unit tests across live-wrap.test.mjs and live-accept.test.mjs
  covering the Fragment-replacement design, both leading/trailing
  template-literal placements, --text disambiguation, the dynamic-
  content fallback, and the element_ambiguous error shape.
- New `runtime.assertSourceContains` fixture hook so other regression
  fixtures can assert sibling-branch survivability cheaply.

All 186 unit + static-fixture tests pass; all 21 live e2e fixtures
(20 prior + new TSX) pass with no console errors.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/live-e2e.test.mjs

@@ -269,6 +269,19 @@ for (const { name, fixture } of fixtures) {
           'accepted h1 survives with hero-title class',
         );
 
+        // Optional fixture hook: assert that arbitrary strings survive the
+        // wrap → accept → carbonize cycle. Used by repeated-branch fixtures
+        // to prove wrap disambiguated correctly — sibling branches the test
+        // didn't pick should be untouched.
+        if (Array.isArray(fixture.runtime.assertSourceContains)) {
+          for (const needle of fixture.runtime.assertSourceContains) {
+            assert.ok(
+              final.includes(needle),
+              `source still contains ${JSON.stringify(needle)} after accept (sibling branch must not be rewritten)`,
+            );
+          }
+        }
+
         // 9. DOM-side: at least one matching element, none inside any wrapper.
         await page.waitForFunction(
           (sel) => {