feat(ui): implement refreshed UX for Composer layout

- Promotes refreshed multi-row status area and footer as the default experience.
- Stabilizes Composer row heights to prevent layout 'jitter' during typing and model turns.
- Unifies active hook status and model loading indicators into a single, stable Row 1.
- Refactors settings to use backward-compatible 'Hide' booleans (ui.hideStatusTips, ui.hideStatusWit).
- Removes vestigial context usage bleed-through logic in minimal mode to align with global UX direction.
- Relocates toast notifications to the top status row for improved visibility.
- Updates all CLI UI snapshots and architectural tests to reflect the stabilized layout.

scripts/changed_prompt.js

@@ -14,17 +14,18 @@ const EVALS_FILE_PREFIXES = [
 function main() {
   const targetBranch = process.env.GITHUB_BASE_REF || 'main';
   try {
-    const remoteUrl = process.env.GITHUB_REPOSITORY
-      ? `https://github.com/${process.env.GITHUB_REPOSITORY}.git`
-      : 'origin';
-
-    // Fetch target branch from the remote.
-    execSync(`git fetch ${remoteUrl} ${targetBranch}`, {
+    // Fetch target branch from origin.
+    execSync(`git fetch origin ${targetBranch}`, {
       stdio: 'ignore',
     });
 
-    // Get changed files using the triple-dot syntax which correctly handles merge commits
-    const changedFiles = execSync(`git diff --name-only FETCH_HEAD...HEAD`, {
+    // Find the merge base with the target branch.
+    const mergeBase = execSync('git merge-base HEAD FETCH_HEAD', {
+      encoding: 'utf-8',
+    }).trim();
+
+    // Get changed files
+    const changedFiles = execSync(`git diff --name-only ${mergeBase} HEAD`, {
       encoding: 'utf-8',
     })
       .split('\n')