Merge block HTML and editor validation into a single validate_blocks tool

[youknowriad]

Related issues

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How AI was used in this PR

Authored end-to-end with Claude Code: consolidated the two validation tools, updated the system prompt and skills, migrated tests, and verified with lint, typecheck, and the tools test suite. Reviewers should sanity-check the gating logic in apps/cli/ai/tools/validate-blocks.ts and the updated agent guidance.

Proposed Changes

The agent previously had to call two separate tools to validate block content — validate_html_blocks (a fast static core/html policy check) followed by validate_and_fix_blocks (live-editor validation that needs a running site). Since the overwhelmingly common case is content that's already valid, this cost two agent turns where one would do.

This merges them into a single validate_blocks tool. The static HTML policy check runs first and acts as a short-circuit gate:

• If it finds invalid core/html blocks, the tool returns only that report and skips live-editor validation entirely — so the agent rewrites those blocks before paying the expensive browser round-trip, exactly as before.
• Once the policy check passes, live-editor validation/fix runs and both reports are concatenated into one result.

User impact: fewer agent turns (and less waiting) on the happy path when generating site content, with no change to the gating behavior that keeps invalid HTML blocks from reaching the editor. One trade-off: the static HTML check is now fused with editor validation, so it requires a running site — in practice it always preceded editor validation anyway.

Testing Instructions

1. npm run cli:build
2. In a studio code session, generate or edit page/post block content and observe that a single validate_blocks call replaces the previous two-call sequence.
3. Provide content containing an invalid core/html block (e.g. a <form>); confirm the tool reports the invalid HTML blocks and does not run editor validation until they're rewritten.
4. Provide valid content; confirm the combined report shows the HTML policy summary followed by editor validation, with auto-fix applied to the file when filePath is passed.

Automated: npm test -- apps/cli/ai/tests/tools.test.ts (48 passing), plus npm run typecheck and npx eslint.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wpmobilebot]

📊 Performance Test Results

Comparing fd7069f vs trunk

app-size

Metric	trunk	fd7069f	Diff	Change
App Size (Mac)	1358.10 MB	1358.10 MB	0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	fd7069f	Diff	Change
load	1744 ms	1745 ms	+1 ms	⚪ 0.0%

site-startup

Metric	trunk	fd7069f	Diff	Change
siteCreation	9523 ms	9039 ms	484 ms	🟢 -5.1%
siteStartup	4416 ms	4412 ms	4 ms	⚪ 0.0%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)