fix: create strategy branch before first commit, not at execute-phase (#1278)

When branching_strategy is "phase" or "milestone", the branch was only
created during execute-phase — but discuss-phase, plan-phase, and
new-milestone all commit artifacts before that, landing them on main.

Move branch creation into cmdCommit() so the strategy branch is created
at the first commit point in any workflow. execute-phase's existing
handle_branching step becomes a harmless no-op (checkout existing branch).

Also fixes websearch test mocks broken by #1276 (fs.writeSync change).

Closes #1278

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/commands.test.cjs

@@ -1185,6 +1185,71 @@ describe('commit command', () => {
     const logCount = execSync('git log --oneline', { cwd: tmpDir, encoding: 'utf-8' }).trim().split('\n').length;
     assert.strictEqual(logCount, 2, 'should have 2 commits (initial + amended)');
   });
+  test('creates strategy branch before first commit when branching_strategy is milestone', () => {
+    // Configure milestone branching strategy
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({
+        commit_docs: true,
+        branching_strategy: 'milestone',
+        milestone_branch_template: 'gsd/{milestone}-{slug}',
+      })
+    );
+    // getMilestoneInfo reads ROADMAP.md for milestone version/name
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '## v1.0: Initial Release\n\n### Phase 1: Setup\n'
+    );
+
+    // Create a file to commit
+    fs.writeFileSync(path.join(tmpDir, '.planning', 'test-context.md'), '# Context\n');
+
+    const result = runGsdTools('commit "docs: add context" --files .planning/test-context.md', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.strictEqual(output.committed, true, 'should have committed');
+
+    // Verify we're on the strategy branch
+    const { execFileSync } = require('child_process');
+    const branch = execFileSync('git', ['rev-parse', '--abbrev-ref', 'HEAD'], { cwd: tmpDir, encoding: 'utf-8' }).trim();
+    assert.strictEqual(branch, 'gsd/v1.0-initial-release', 'should be on milestone branch');
+  });
+
+  test('creates strategy branch before first commit when branching_strategy is phase', () => {
+    // Configure phase branching strategy
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({
+        commit_docs: true,
+        branching_strategy: 'phase',
+        phase_branch_template: 'gsd/phase-{phase}-{slug}',
+      })
+    );
+    // Create ROADMAP.md with a phase
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-setup'), { recursive: true });
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '# Roadmap\n\n## Phase 1: Setup\nGoal: Initial setup\n'
+    );
+
+    // Create a context file for phase 1
+    fs.writeFileSync(path.join(tmpDir, '.planning', 'phases', '01-setup', '01-CONTEXT.md'), '# Context\n');
+
+    const result = runGsdTools(
+      'commit "docs(01): add context" --files .planning/phases/01-setup/01-CONTEXT.md',
+      tmpDir
+    );
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.strictEqual(output.committed, true, 'should have committed');
+
+    // Verify we're on the strategy branch
+    const { execFileSync } = require('child_process');
+    const branch = execFileSync('git', ['rev-parse', '--abbrev-ref', 'HEAD'], { cwd: tmpDir, encoding: 'utf-8' }).trim();
+    assert.strictEqual(branch, 'gsd/phase-01-setup', 'should be on phase branch');
+  });
 });
 
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