Prepare v0.5.0 release

[moneycaringcoder]

Summary

Prepares the Mission Control feature release as Tether v0.5.0.

Release surfaces

• Bumps the crate, lockfile, and Herdr plugin manifest to 0.5.0.
• Publishes the Mission Control changelog under the dated 0.5.0 heading.
• Pins stable plugin, standalone CLI, documentation, and Hermes skill URLs to v0.5.0.
• Updates the plugin manifest contract and CI release-candidate identity check.

Local verification

• cargo fmt --all -- --check
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --all-targets --all-features -- --test-threads=1 — 387 tests passed
• cargo build --release --locked
• cargo +1.88.0 check --locked --all-targets --all-features
• Python quality suites — 78 tests passed
• Documentation, v0.5.0 candidate identity, package, and public-contract checks
• Package contents — 54 files; 23 curated public examples