feat(cli): add --json global flag for structured output

[Pavel Feldman (pavelfeldman)]

Summary

• New global --json flag: every playwright-cli reply is a single pretty-printed JSON document on stdout (local commands and every MCP tool command).
• Plumbed through MCP via _meta.json alongside _meta.cwd and _meta.raw; implies --raw.
• Refactors CLI rendering into an Output interface with TextOutput / JsonOutput implementations — removes all if (json) ... else ... branching from program.ts and strips console.log from session.ts.
• Docs: new skill/references/json-output.md reference.

[Dmitry Gozman (dgozman)]

I like the mcp Response with sections more than this interface...

[github-actions]

Test results for "MCP"

14 failed
❌ [chromium] › mcp/cli-json.spec.ts:84 › list after open returns one browser entry @mcp-ubuntu-latest
❌ [chrome] › mcp/cli-json.spec.ts:75 › open returns envelope with session, pid and snapshot file @mcp-windows-latest
❌ [chrome] › mcp/cli-json.spec.ts:103 › goto returns snapshot file envelope @mcp-windows-latest
❌ [chromium] › mcp/cli-json.spec.ts:75 › open returns envelope with session, pid and snapshot file @mcp-windows-latest
❌ [chromium] › mcp/cli-json.spec.ts:84 › list after open returns one browser entry @mcp-windows-latest
❌ [chromium] › mcp/cli-json.spec.ts:103 › goto returns snapshot file envelope @mcp-windows-latest
❌ [firefox] › mcp/cli-json.spec.ts:75 › open returns envelope with session, pid and snapshot file @mcp-windows-latest
❌ [firefox] › mcp/cli-json.spec.ts:103 › goto returns snapshot file envelope @mcp-windows-latest
❌ [firefox] › mcp/cli-test.spec.ts:23 › debug test and snapshot @mcp-windows-latest
❌ [chromium] › mcp/cli-json.spec.ts:84 › list after open returns one browser entry @mcp-macos-latest
❌ [webkit] › mcp/cli-json.spec.ts:75 › open returns envelope with session, pid and snapshot file @mcp-windows-latest
❌ [webkit] › mcp/cli-json.spec.ts:103 › goto returns snapshot file envelope @mcp-windows-latest
❌ [msedge] › mcp/cli-json.spec.ts:75 › open returns envelope with session, pid and snapshot file @mcp-windows-latest
❌ [msedge] › mcp/cli-json.spec.ts:103 › goto returns snapshot file envelope @mcp-windows-latest

6355 passed, 976 skipped

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Merge workflow run.