v0.84.0

Added

• synapse completions <shell> prints a static tab-completion script for bash, zsh, or
  fish. The script is generated from the installed CLI's live argument parser — top-level
  subcommands, nested subcommands, and long options — so it cannot drift from the surface
  it completes, needs no extra dependency, and starts no process per keystroke. Install it
  where the shell looks for completions (or evaluate it inline) and re-run the command
  after an upgrade to refresh it.

Changed

• synapse doctor --fix now auto-repairs the safely repairable findings instead of only
  printing setup commands: when the default local hub does not answer or the identity's
  waiter is missing, it installs and starts the local hub, presence, and wake-arming user
  services, then re-runs the checks so the exit code reports the post-repair state. The
  repair is gated to the default loopback hub the generated services manage — a remote or
  non-default hub is never touched; its findings keep printed guidance, as do identity,
  exposure, and disk findings.
• synapse hub --federation-store now refuses to start when the store's peerings grant
  cross-domain scope but --require-message-auth is not set: without per-message
  authentication no signing key is ever verified, so the granted scope could never be
  enforced and every cross-domain frame would be silently refused. A store whose peerings
  grant no enforceable scope still starts with the existing warning, and the new
  --federation-observe-only flag declares the intent to load a scope-granting store for
  diagnostics and deny-closed refusal only; combining it with --require-message-auth,
  or passing it without a store, is refused as contradictory.