Homepage: consolidate sections and apply design copy edits - #744

Implements the Homepage.dc.html design from the Claude Design handoff.

Structure:
- Merge "The README as a CLI." and "Stop hoping the agent reads the
  instructions." into one compact "Make instructions executable." section
  with two equal columns.
- Delete "The runtime handles the effects." and its Repository/Worktree
  example; move the component-resolution sentence into "Agents pass values."
- Retitle "The nesting is the model." to "The runtime owns the workflow.",
  replacing the per-line TempDir walkthrough with three runtime-semantic
  paragraphs.
- Lift the star CTA out of the install card into its own section.

Copy:
- Hero leads with "Turn what you've done before into a program" and drops
  readability as a product claim.
- Hero panel leads with "Markdown describes the workflow."
- "Schemas make answers usable." becomes "Schemas make judgment usable.",
  collapsing the Json/Parse/Elicit walkthrough the example already teaches.

Removes README_MD, AGENTS_MD, IMPLEMENTOR_MD and SCOPES_MD, now unused.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_014idQZxeQCcKgtbVwC1pH42

Implements the revised Homepage.dc.html from Claude Design, on top of the
earlier consolidation.

Copy:
- Hero headline is "Minimize agentic work."; the standfirst drops the
  prose-vs-program setup and states the thesis directly.
- The hero panel is now just the example. Its release.md is rewritten to a
  plain <Prompt> over two <File> reads, replacing the Let/Parse/Json/Publish
  schema walkthrough, and runs `npm test` rather than `deno task test`.
- "The point" panel becomes "Use the least autonomy that gets the job done."
- The plan section keeps two paragraphs instead of three.
- The component-resolution sentence moves out of "Agents pass values." into
  its own "Build your own components." block.

Structure:
- "Plans are made to be followed." moves ahead of "The runtime composes
  intent.", so the plan story lands before the runtime detail.
- Plan panels become titled CLI / XMD source panels with the instruction
  wrapping carried in the example, replacing the eyebrow-labelled terminal
  slab and its hanging-indent CSS.

Copy-to-clipboard:
- CodeBlock gains an opt-in `copy` affordance. One delegated listener on the
  page serves every panel, so 16 panels cost one listener rather than an
  island each. Docs and designing-workflows are unaffected.

Also fixes a latent bug: `#plan strong code{font-weight:800}` never applied,
because Term sets font-weight inline and no selector can outrank that. Term
gains a `heavy` variant that puts the weight on the element instead.

External links now carry target="_blank", and the homepage title and
description match the design's.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_014idQZxeQCcKgtbVwC1pH42