Fix block registry metadata extraction

[Maya-Kid]

Why

The registry describes agent-workspace as the dashboard that follows it. Its multiline description does not match the generator's single-line expression, which then searches through the remaining entries.

What changes

Read each literal block object with the existing TypeScript parser, so formatting, comments and neighbouring entries cannot change its title or description. Missing or dynamic metadata and duplicate block names fail explicitly. Also reject repeated metadata keys and spread/computed properties that could override a literal at runtime, with the block's source line in the error. Provably unrelated static keys and literal spreads remain supported.

Regenerate the workspace description and run the targeted parser regressions in CI.

How it was checked

• Eight Node regression tests: real multiline metadata; formatting, escapes and nesting; missing fields; dynamic values and duplicate names; runtime spread/computed overrides; repeated keys; unrelated static properties; invalid syntax and nonliteral members.
• npm run docs, npm run typecheck and npm run build pass after the review fixes. The generated registry remains unchanged after regeneration.
• Both source and served registry JSON contain the workspace description; the only registry diff is that description.
• Chromium 155: /dev/examples reports 389/389 mounted and 0 failed in both themes, without page errors.
• Earlier targeted checks inspected the workspace in both themes, including the expanded file diff and mode menu.

Before review

• Every commit is signed off (git commit -s)
• npm run typecheck and npm run build pass
• /dev/examples reports 0 failed
• What the change touches was looked at in both themes, open states included