feat(p8): vue IDE /workspace (arbre + Monaco + diff + terminal)

- backend: garde-fou conflit d'édition par mtime (GET renvoie mtime, PUT refuse en 409 STALE_FILE si baseMtime périmé)
- lib: wt-key (base64url du chemin worktree), diff-parse (parseur pur du diff unifié → hunks)
- composables: useMonaco (import dynamique → chunk isolé), useWorkspaceLayout (largeurs/panneau persistés)
- components/workspace: GitStatusBadge, FileTree+FileTreeNode (lazy fs/list includeFiles), ChangedFilesPanel, DiffViewer (coloration +/-), MonacoEditor (Ctrl+S + bannière conflit reload/overwrite)
- views/WorkspaceView: 3 colonnes desktop redimensionnables + SegmentedControl mobile, header live (GitStatusBadge), watchWorktree → refresh diff/changements, terminal de la session corrélée
- router meta 'ide' + route /workspace/:repoId/:wt ; App.vue plein écran sans AppShell ; WorktreeCard bouton « Ouvrir l'IDE »
- deps: monaco-editor (lazy, vendor-monaco isolé, 0 impact bundle initial) ; vite manualChunks
- i18n EN+FR (workspace/editor/diff/git) ; tests diff-parse + wt-key ; acceptance-p8.mjs (mtime/409 + diff)

packages/web/test/diff-parse.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it } from 'vitest';
+import { parseUnifiedDiff } from '../src/lib/diff-parse';
+
+const SAMPLE = `diff --git a/README.md b/README.md
+index 1234567..89abcde 100644
+--- a/README.md
++++ b/README.md
+@@ -1,3 +1,4 @@
+ # demo
++edited line
+ second
+-old third
++new third
+@@ -10,2 +11,2 @@
+ ten
+-eleven
++ELEVEN`;
+
+describe('parseUnifiedDiff', () => {
+  it('ignore les en-têtes de fichier avant le premier @@', () => {
+    const r = parseUnifiedDiff(SAMPLE);
+    expect(r.hunks).toHaveLength(2);
+    expect(r.hunks[0].header).toBe('@@ -1,3 +1,4 @@');
+  });
+
+  it('compte additions et suppressions', () => {
+    const r = parseUnifiedDiff(SAMPLE);
+    expect(r.additions).toBe(3); // edited line, new third, ELEVEN
+    expect(r.deletions).toBe(2); // old third, eleven
+  });
+
+  it('numérote correctement les lignes ancien/nouveau', () => {
+    const { hunks } = parseUnifiedDiff(SAMPLE);
+    const lines = hunks[0].lines;
+    expect(lines[0]).toMatchObject({ type: 'context', content: ' # demo'.slice(1), oldLine: 1, newLine: 1 });
+    const add = lines.find((l) => l.type === 'add');
+    expect(add).toMatchObject({ oldLine: null, newLine: 2, content: 'edited line' });
+    const del = lines.find((l) => l.type === 'del');
+    expect(del).toMatchObject({ newLine: null, content: 'old third' });
+  });
+
+  it('ignore le marqueur « \\ No newline at end of file »', () => {
+    const diff = `@@ -1 +1 @@\n-a\n+b\n\\ No newline at end of file`;
+    const r = parseUnifiedDiff(diff);
+    expect(r.additions).toBe(1);
+    expect(r.deletions).toBe(1);
+    expect(r.hunks[0].lines).toHaveLength(2);
+  });
+
+  it('diff vide → aucun hunk', () => {
+    expect(parseUnifiedDiff('').hunks).toHaveLength(0);
+  });
+
+  it('gère un fichier untracked (--- /dev/null)', () => {
+    const diff = `--- /dev/null\n+++ b/new.txt\n@@ -0,0 +1,2 @@\n+line one\n+line two`;
+    const r = parseUnifiedDiff(diff);
+    expect(r.additions).toBe(2);
+    expect(r.hunks[0].lines.every((l) => l.type === 'add')).toBe(true);
+  });
+});

packages/web/test/wt-key.test.ts

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+import { describe, expect, it } from 'vitest';
+import { encodeWtKey, decodeWtKey } from '../src/lib/wt-key';
+
+describe('wt-key (base64url)', () => {
+  const paths = [
+    '/home/johan/WebstormProjects/arboretum',
+    '/srv/code/feature-branch',
+    '/tmp/with space/and-dash',
+    '/projets/accentué/café/é',
+    '/a/b/c/d/e/f/g',
+  ];
+
+  it('round-trip encode → decode pour divers chemins', () => {
+    for (const p of paths) expect(decodeWtKey(encodeWtKey(p))).toBe(p);
+  });
+
+  it('produit un segment d’URL sûr (pas de + / =)', () => {
+    for (const p of paths) {
+      const key = encodeWtKey(p);
+      expect(key).not.toMatch(/[+/=]/);
+      expect(encodeURIComponent(key)).toBe(key); // déjà URL-safe
+    }
+  });
+});