Plaza is 0.4.0

[sepehr-safari]

Version bump and release notes for v0.4.0.

Everything in it is the read side of the outbox, plus the docs that had stopped describing it:

• #204 a relay that has answered nothing cannot be asked for the last hour
• #205 ask each relay about the people who write there, not about everyone
• #206 choose relays by who they reach, not by how popular they are
• #207 keep the sockets you already have
• #208 eight routes, not four
• #209 say where the feed comes from

The nostr library is unchanged at v0.8.0.

Checked before tagging

• Full suite green, and the three guards from Keep the sockets you already have #207 re-probed at the new budget.
• scripts/frame-budget.sh inside every budget: rebuild 275us of 600, layout 1360us of 2200, patch 55us of 150.
• Ran the release build against my own account for several minutes, reading only. No panics, one relay refusing a handshake and reconnecting on its ladder, 41 threads and 237 MB with eight routed connections up.
• Packaged and verified the artifact: arm64, CFBundleShortVersionString 0.4.0, ad-hoc signature verifies --deep --strict, and no automation-server markers in any of the four binaries.