docs: update agent chart contract

[malinskibeniamin]

Description

Updates the agent chart guide to match the current Inspector chart contract.

• Documents the strict JSON contract for bar and line charts, including the top-level title field.
• Clarifies that the Inspector renders with shadcn/Recharts; Chart.js appears only in compatibility and migration guidance.
• Explains compatibility for existing Chart.js-shaped bar and line blocks.
• Replaces unsupported Chart.js types and options with migration guidance.
• Removes obsolete zoom, pan, and PNG export instructions.
• Replaces the rendered-chart screenshot with the current Chart, Data, and Code UI.
• Applies direct actions, specific recovery guidance, and accessible image descriptions.

User impact

Agent builders get an accurate prompt example and a direct migration path. Existing bar and line blocks remain documented as compatible; unsupported chart types have explicit conversion guidance.

Checks

• Local Antora build (npm run build)
• Updated page parses as AsciiDoc and its migration anchor resolves
• Verified the replacement screenshot

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🔨 Latest commit	9ad93f7

[micheleRP]

Thanks for this. I pushed 9ad93f7 with follow-up edits rather than leaving more suggestions, since several of my earlier ones had gone stale against your latest commit.

The chart contract itself checks out. Verified against the renderer: the JSON schema, the bar and line restriction, the top-level title field, the legacy title fallback, the error and placeholder strings, and that zoom, pan, and PNG export are genuinely gone. All accurate, and the migration table is the right structure for this change.

What Claude changed, and why:

Terminology. The page now says Agentic Data Plane instead of Redpanda Cloud. Agentic Data Plane runs standalone at ai.redpanda.com, and the Inspector and its chart components belong to it, so framing this as a Cloud dependency isn't right. This also replaces "the current chart contract" with "the Agentic Data Plane chart contract". Naming it keeps the page accurate the next time the contract changes, where "current" would quietly go stale.

Page title. Restored to title case, "Draw Charts from an Agent". Our style guide uses sentence case for H2 and below only; page titles stay title case, and the nav entry already read "Draw Charts from an Agent".

Learning objectives. Reduced from four to three, which is our maximum. "Emit a chart code block" is folded into the instruct objective.

Troubleshooting table. "Unsupported chart type" is the description inside the Failed to render chart error rather than a separate error, so that row is reworded. The three error and status strings are also unbolded, since we reserve bold for buttons, tabs, and other click targets.

Inspector walkthrough. The example prompt now matches the screenshot, and the image description names the chart it actually shows.

Two things for next time: spell out whole numbers one through nine in prose, and keep the source citation comment at the top of the page pointing at the files you verified against. That comment is how the next person re-checks the page.

[micheleRP]

thank you @malinskibeniamin