fix(install): let Skip in the AI CLI menu continue instead of aborting the install

Choosing "s" (Skip) in the new catalogue-driven install menu warned, printed the
install hints and then fell into the shared "The selected AI CLI failed to install"
gate one line below, because CLI_FOUND_COUNT is 0 by construction inside that block
and skipping does not change it. The AI CLI check runs before the clone and the
build, so a user who picked the documented skip option ended up with nothing
installed. The code this replaced guarded the gate with an elif on the skip choice.

The menu moves out of main() into offer_ai_cli_install() and the gate moves inside
the install branch: skipping continues to the clone, a chosen install that leaves
nothing behind is still fatal. Being a function, the interactive path can now be
driven with a stubbed read_reply, which is what nothing reached before: two
behavioural tests in test/install-sh-invariants.test.ts run the real function in a
real bash (skip continues with exit 0, a failed install dies with exit 1), and the
bash 3.2 CI step drives the skip path in the container as well.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

test/install-sh-invariants.test.ts

@@ -11,10 +11,12 @@
  */
 
 import { describe, expect, it } from 'vitest';
+import { spawnSync } from 'node:child_process';
 import { readFileSync } from 'node:fs';
 import { fileURLToPath } from 'node:url';
 
-const SOURCE = readFileSync(fileURLToPath(new URL('../install.sh', import.meta.url)), 'utf-8');
+const INSTALL_SH = fileURLToPath(new URL('../install.sh', import.meta.url));
+const SOURCE = readFileSync(INSTALL_SH, 'utf-8');
 
 /** Lines with the leading `#` comments removed, so prose quoting a banned form is not a hit. */
 const CODE_LINES = SOURCE.split('\n').filter((line) => !/^\s*#/.test(line));
@@ -164,3 +166,64 @@ describe('install.sh runtime safety', () => {
     expect(SOURCE).toMatch(/^set -euo pipefail$/m);
   });
 });
+
+describe('install.sh AI CLI install menu', () => {
+  // The menu is the one interactive path in the script, which is why it used to be the
+  // only part nothing exercised: choosing "s" (Skip) once fell straight into the shared
+  // "failed to install" gate and aborted the installer before the clone. These drive the
+  // real function (offer_ai_cli_install) in a real bash, with detection pointed at
+  // nothing so the menu appears, and read_reply scripted.
+  const DRIVER = `
+    set -euo pipefail
+    export CODEMAN_INSTALL_SH_LIB=1
+    . "$1"
+    k=0; while [[ $k -lt \${#CLI_ALL_BINS[@]} ]]; do CLI_ALL_BINS[$k]="codeman-test-no-such-bin-$k"; k=$((k + 1)); done
+    k=0; while [[ $k -lt \${#CLI_ALL_PATHS[@]} ]]; do CLI_ALL_PATHS[$k]="/nonexistent/codeman-test/$k"; k=$((k + 1)); done
+    if [[ -n "\${MENU_INSTALL_CMD:-}" ]]; then
+      k=0; while [[ $k -lt \${#CLI_INSTALL_CMD_TRUSTED[@]} ]]; do CLI_INSTALL_CMD_TRUSTED[$k]="$MENU_INSTALL_CMD"; k=$((k + 1)); done
+    fi
+    CLI_DETECT_DONE=""
+    detect_all_clis
+    echo "found=$CLI_FOUND_COUNT"
+    NONINTERACTIVE=0
+    DOWNLOADER=curl
+    has_tty() { return 0; }
+    headless_guard() { return 0; }
+    read_reply() { eval "$1=\\"$MENU_ANSWER\\""; }
+    offer_ai_cli_install
+    echo "REACHED THE STEP AFTER THE MENU"
+  `;
+
+  function driveMenu(answer: string, installCommand?: string) {
+    const result = spawnSync('bash', ['-c', DRIVER, 'bash', INSTALL_SH], {
+      encoding: 'utf-8',
+      timeout: 30_000,
+      env: { ...process.env, MENU_ANSWER: answer, ...(installCommand ? { MENU_INSTALL_CMD: installCommand } : {}) },
+    });
+    // eslint-disable-next-line no-control-regex
+    const strip = (s: string) => s.replace(/\x1b\[[0-9;]*m/g, '');
+    return { status: result.status, stdout: strip(result.stdout ?? ''), stderr: strip(result.stderr ?? '') };
+  }
+
+  it('offers the menu only when nothing is installed', () => {
+    const run = driveMenu('s');
+    expect(run.stdout).toContain('found=0');
+    expect(run.stderr).toContain('Choose [1-');
+  });
+
+  it('continues past the menu when the user skips', () => {
+    const run = driveMenu('s');
+    expect(run.stderr).toContain('Skipping AI CLI install');
+    expect(run.stdout, run.stderr).toContain('REACHED THE STEP AFTER THE MENU');
+    expect(run.stderr).not.toContain('failed to install');
+    expect(run.status).toBe(0);
+  });
+
+  it('still dies when the chosen install leaves nothing behind', () => {
+    const run = driveMenu('1', 'false');
+    expect(run.stderr).toContain('installation failed');
+    expect(run.stderr).toContain('The selected AI CLI failed to install');
+    expect(run.stdout).not.toContain('REACHED THE STEP AFTER THE MENU');
+    expect(run.status).toBe(1);
+  });
+});