Rivet 0.9.0

• Close the last below-floor commercial capability gap with first-party
  native file dialogs on every desktop platform. Windows uses Common Item
  Dialogs, macOS uses asynchronous AppKit panels, and Linux uses GTK4 native
  choosers with portal delegation. The adapters cover open, save, folder
  selection, extension filters, cancellation, and open-file multi-selection
  without adding file-picker traffic to RVT1.

• Make Linux a first-class product target everywhere users discover Rivet:
  the English and Chinese READMEs now include its badge, requirements,
  positioning, and comparison stack; the bilingual landing page includes
  GTK4 in both the native-UI feature card and comparison table; and the stale
  unsupported-host remediation no longer claims only Windows and macOS can
  build. Documentation tests pin all three targets to prevent this class of
  omission from returning.

• Fix source-package smoke tests under set -o pipefail. Archive entries are
  now read once and checked from a file, so grep -q cannot close a repeated
  unzip pipeline early and turn a successful match into spurious exit 141.
  Source releases also explicitly omit native build/output trees (the Racket
  packager does not read .gitignore), and the isolated install overrides any
  maintainer-machine installation-scope link instead of producing a false
  “already installed” result.

• Add first-party plain-text clipboard read/write/change observation across
  every desktop adapter. macOS uses NSPasteboard with main-run-loop
  changeCount polling, Windows uses CF_UNICODETEXT plus a message-only
  clipboard owner and WM_CLIPBOARDUPDATE, and Linux uses GTK4/GDK with
  asynchronous reads suitable for Wayland ownership transfers. Native
  observation stays on the platform UI thread and outside RVT1.

• Complete cross-platform global shortcuts. Linux already binds through the
  XDG portal; macOS gains RivetGlobalShortcuts (Carbon
  RegisterEventHotKey, main-thread event loop, explicit duplicate-trigger
  refusal — RegisterHotKey provides it on Windows, Carbon does not) and
  Windows gains rivet::system::GlobalShortcuts (RegisterHotKey on a
  message-only window with WM_HOTKEY dispatch). The three adapters share
  one activation-callback shape (shortcut id, millisecond timestamp,
  portal-only activation token) and direct-registration platforms share a
  case-insensitive trigger grammar; ANSI virtual-key codes map through
  their Carbon constants because the codes follow the physical QWERTY
  layout, not the alphabet. macOS parse and lifecycle tests are in the
  Swift suite; the Windows adapter is compile-gated by the WinUI CI host
  build.

• Add docs/commercial-parity.md: the honest scorecard against the Tauri 2
  and Electron feature floors (above / at / below / roadmap per
  capability), with rules of engagement — a product hand-rolling the same
  capability twice is a library gap, below-floor rows outrank new surface
  area, and the docs suite keeps the scorecard's tracked capability rows
  (global shortcuts, clipboard, native file dialogs, mobile hosts) from
  silently disappearing.

• Close the scribble coverage gap: the RVT1 framing and value-codec surface
  (rivet/protocol — frames, message-type constants, transport limits,
  read/write/encode/decode), application resources (rivet/resources),
  the diagnostic sink parameter, install-crash-hook!, the version
  predicates, the Ed25519 key/digest/base64 primitives, canonical manifest
  payload helpers, verify-update-artifact!, make-install-plan,
  current-install-kind, and the missing updater? predicate now have
  manual entries. Every public export is covered and the rendered manual
  carries no undefined-tag warnings.

• Documentation drift now fails CI instead of rotting silently. The docs
  suite derives the current release version from info.rkt and rejects a
  docs/ci*.md guide pinning any other tag, and it checks scribble
  coverage in both directions: a public export without a manual mention
  fails, and a manual entry for a binding that is no longer exported fails
  (defstruct* forms synthesize their constructor, predicate, structure-type
  binding, and accessors, mirroring the rendered output).