Disable telemetry in standalone local integration scripts

[sdairs]

Summary

• Export DO_NOT_TRACK=1 at the standalone Postgres integration script boundary before it invokes clickhousectl.
• Add a subprocess test that starts with DO_NOT_TRACK=0, runs the script against fake CLI/Docker/jq executables, and proves every spawned CLI inherits DO_NOT_TRACK=1.
• Keep telemetry behavior and telemetry E2E coverage unchanged; those tests continue to remove the opt-out only while targeting their local wiremock endpoint.

Audit

• scripts/test-postgres-integration.sh is the only executable repository integration/evaluation script that invokes clickhousectl; it is now protected at its own boundary.
• scripts/check-openapi-drift.py invokes the Rust analyzer, not clickhousectl; the other scripts/*.py files do not launch the CLI.
• install.sh installs the binary without executing it. npm/bin/cli.js is the user-facing product shim, not a repository test boundary, so it intentionally preserves user telemetry choices.
• Every repository workflow already exports DO_NOT_TRACK=1; no workflow change is needed.

Tests

• python3 -m unittest discover -s scripts/tests (44 passed)
• python3 -m unittest scripts.tests.test_script_telemetry (1 passed)
• bash -n scripts/test-postgres-integration.sh
• shellcheck scripts/test-postgres-integration.sh
• cargo test -p clickhousectl (768 passed)
• cargo test -p clickhousectl --test telemetry_test (21 passed)
• cargo clippy -p clickhousectl --all-targets -- -D warnings
• cargo fmt --all --check
• Real Docker battery not run locally: the configured OrbStack daemon socket is absent. The child local postgres edge cases CI check covers it.

Stack

Position 5 of 5 (top), based on #509.

• Validate local Postgres start options before Docker work #486 validates local Postgres start options before Docker work.
• Wait for PostgreSQL readiness before local start success #498 waits for PostgreSQL readiness before reporting startup success.
• Make local Postgres startup transactional #501 makes fresh startup transactional across Docker start, metadata persistence, and readiness.
• Correct local Postgres diagnostics and help #509 corrects Postgres and Docker diagnostics and pins the rendered help contract.
• This PR disables repository-test telemetry at the standalone script boundary.

Closes #458

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