Provides a self-contained reproducer for the new sapi_module.activate /
deactivate hooks added in src/debugger/frankenphp.c.

- tests/frankenphp/Dockerfile: multi-stage build that compiles
  php_debugger.so against FrankenPHP's bundled ZTS PHP and installs it
  as a Zend extension with xdebug.mode=debug and start_with_request=trigger.
- tests/frankenphp/Caddyfile: minimal config registering /app/worker.php
  as the FrankenPHP worker, with explicit http:// scheme to avoid the
  default auto-https redirect.
- tests/frankenphp/app/{worker.php,index.php}: long-lived
  frankenphp_handle_request() loop and a sample request script with an
  obvious breakpoint location.
- tests/frankenphp/entrypoint.sh: rewrites xdebug.client_host /
  xdebug.client_port from XDEBUG_CLIENT_HOST / XDEBUG_CLIENT_PORT env
  vars before exec'ing FrankenPHP (PHP INI has no native fallback
  syntax for env-var defaults).
- tests/frankenphp/README.md: build/run instructions, one-time PhpStorm
  Server + path-mapping setup, the four verification scenarios
  (no-trigger skip, trigger pause, multi-request worker reuse, and the
  xdebug_dbgp_poll_pending breakpoint-between-requests test), and a
  troubleshooting table.
- .dockerignore: keeps host build artifacts (Makefile, *.dep, *.lo,
  .libs, ...) out of the build context — without this, absolute host
  paths baked into the local Makefile break the in-container build.
- .gitignore: adds tests/frankenphp/**/*.{php,sh} allowlist exceptions
  so the test files aren't swallowed by the blanket *.php / *.sh rules
  used to ignore stray test artifacts.

Three coupled changes are needed for line breakpoints to fire on
functions called by trigger requests after non-trigger requests have run
in the same worker:

1. xdebug_observer_init: always return real handlers. The Zend engine
   caches the result per zend_function the first time the function is
   observed, so returning {NULL, NULL} when observer_active=false
   permanently blacklists that function — even after a debugger
   connects in a later request that reuses the cached op_array. The
   handlers themselves already fast-path on \!observer_active, so the
   no-debug overhead remains a single load+branch.

2. xdebug_frankenphp_sapi_activate: re-arm observer_active per request.
   FrankenPHP runs PHP_RINIT only once at worker startup; per-request
   only sapi_activate fires. Without this, a worker that started with
   no IDE leaves observer_active=false for the rest of its life, so
   xdebug_execute_begin fast-paths out, no fse is pushed, and
   xdebug_debugger_statement_call bails on its empty-stack check.

3. xdebug_frankenphp_minit: force ZEND_COMPILE_EXTENDED_STMT and
   disable the opcache optimizer at MINIT. The normal RINIT path skips
   this when no IDE is connected at startup, but in the worker flow
   user files are compiled later — by trigger requests that need
   EXT_STMT opcodes already present. Without this, breakpoint_set sees
   an empty "set of executable lines" for the target file.

The `tests/frankenphp/app` workload (`workload()` defined in `lib.php`,
called from `index.php`) plus `dbgp_listener.py` reproduce the failure
deterministically: 200 no-trigger requests followed by 5 trigger
requests previously yielded 0/5 breakpoint hits; with the fix all 5
hit lib.php:4.