[clue]

This changeset improves the Docker build times for our recommended Dockerfile by compiling the recommended ext-ev and ext-sockets extensions in parallel build stages instead of a single sequential RUN step. The build toolchain is also narrowed from twelve packages to five and named .phpize-deps, which is the name docker-php-ext-install looks for before installing and purging all ten $PHPIZE_DEPS itself.

build	before	after
production image on a 16-core workstation	21.0s	11.1s
production image on a CI runner	29s	23s

The workstation row is medians of five cold builds per variant, alternating between the two so host load cancels out, with base images pulled beforehand. Spreads were under half a second. The CI row is the Docker job's docker build step across real runs, 10 before spanning 26-41s and 5 after spanning 15-25s.

Along the way this drops the # syntax=docker/dockerfile:1 directive from both Dockerfile instructions, as nothing in them needs the external frontend and fetching it costs a serial registry round-trip on every build.

The resulting image is a strict subset of the previous one: the duplicate libev package is gone, as PECL's ev bundles and static-links its own copy and never linked the system one, along with the /tmp/pear build leftovers the old single-stage build shipped. ext-ev itself is unchanged, and the Dockerfile in our integration tests keeps following the documentation as before.

Builds on top of #297, #207, #156, #149, #136 and https://github.com/clue-engineering/gisthook/pull/129 (private)

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No active review issues are recorded for the production Docker build changes.

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What changed in this PR

This PR speeds up the recommended production Docker build by separating dependency installation and PHP extension compilation into parallel stages, while keeping the integration Dockerfile aligned with the documentation.

Changes:

• Build ext-ev and ext-sockets in separate stages using a smaller shared toolchain.
• Copy compiled extensions into the runtime image without carrying over build tools or temporary files.
• Remove the external Dockerfile syntax directive from both documented examples and integration Dockerfiles.

File	Description
tests/​integration/​Dockerfile-production	Mirrors the parallel extension builds and streamlined production image.
tests/​integration/​Dockerfile-basics	Removes the external syntax directive.
docs/​best-practices/​deployment.md	Documents the parallel production build and updates both Dockerfile examples.

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