Allow astro preview --ignore-lock from AI agent environments

[matthewp]

Changes

• astro preview --ignore-lock and astro dev --ignore-lock no longer error when an AI agent is detected (e.g. CLAUDECODE set in the environment). Agent detection only infers background mode, while --ignore-lock explicitly asks for a one-off foreground server that stop/status/logs won't track — the flag now wins and the server starts in the foreground. This unblocks Playwright's webServer (npx astro preview --ignore-lock --port <port>) when run from an agent session.
• Agent-inferred background is dropped whenever --ignore-lock is set; an explicit --background combined with --ignore-lock still errors, unchanged.
• Fixes astro preview --ignore-lock is refused whenever an AI agent is detected, so Playwright webServer cannot use it from an agent session #17903.

Testing

• Added unit tests for both preview and dev that exercise the CLI path with an agent env var set (CLAUDECODE=1) plus --ignore-lock, asserting a foreground server starts and serves HTTP 200.
• Updated getBackgroundIgnoreLockConflict tests for its new single-argument signature; the previous assertion that agent-implied background conflicts was removed, since that combination no longer errors.

Docs

• No docs update needed: the CLI help text for --ignore-lock is unchanged and still accurate.

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Latest commit: 869b3e9

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[codspeed-hq]

Merging this PR will improve performance by 17.44%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
✅ 20 untouched benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	many-components (markHTMLString, isHTMLString, validateProps)	11.3 ms	9.6 ms	+17.44%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing fix/17903-preview-ignore-lock-agent-gate (869b3e9) with main (42e9188)¹}

Footnotes

1. No successful run was found on main (8eaa4f2) during the generation of this report, so 42e9188 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩