doction 0.32.0

A finished-product pass over the application and https://doction.site, and one visual language
across both: green for the brand and "you are here", orange only for notes. No API or MCP
contract changed.

Added

• The documentation site presents itself when shared or indexed: a robots.txt naming the
  sitemap, a title and description of its own on every page (derived from the page when it
  declares none), a descriptive home title, and Open Graph / Twitter card tags with a social
  image built from the design tokens.
• A 404 in doction's voice on the site, linking Installation, REST API, MCP and Home,
  instead of the framework's generic page.
• The site build checks what it built: it fails, naming the page, when a page lacks its
  title, description or social tags, when robots.txt is missing, or when anything would load
  from another host — the offline guarantee was previously verified by hand.

Changed

• One brand mark, in green. The terminal glyph is --nav-green in the app's sidebar (it
  was orange), and the app's favicon and installable-app icons, still in the retired blue
  palette, now match the documentation site. icon-512.png is full-bleed, as its maskable
  entry requires. theme-color and the manifest use the current canvas and chrome tokens.
  DESIGN.md records the brand mark.
• The app and doction.site assign colour the same way. Green marks the brand and "you
  are here": the active page, table-of-contents entry and settings section carry a 2px green
  rule in the app (it was orange; the green measures 6.92:1 against the active surface), and
  the site's active navigation entry carries the same rule. Orange is left for one job, the
  rule beside quotations and admonitions. Breadcrumb separators are subtle ink.
• The wordmark is "doction" in the sidebar and the webhook help text, as everywhere else.
• The favicon, manifest and touch icon are linked with a content hash, like the stylesheet,
  so a changed icon reaches the browser instead of waiting out its favicon cache.
• A browser address outside the application that matches nothing — /settings,
  /w/x/graph — redirects to the same path under /app instead of answering with raw JSON.
  API clients and requests that do not ask for HTML keep the JSON 404.

Fixed

• Links in running text on the documentation site are underlined, as they are in the app:
  they were distinguished by colour alone (WCAG 1.4.1, reported by axe-core in both themes).