Make broker local negotiation explicit

[wdcui]

Make BrokerLocal negotiated-by-construction so active broker requests cannot run before negotiation.

Remove unrecoverable negotiation-state errors from the public local adapter API.

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

Click for details

--- failure enum_variant_missing: pub enum variant removed or renamed ---

Description:
A publicly-visible enum has at least one variant that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.48.0/src/lints/enum_variant_missing.ron

Failed in:
  variant BrokerLocalError::NotNegotiated, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/3ad27ee7cb31bf14975cd02bd68431e9876e2f76/litebox_broker_local/src/error.rs:14
  variant BrokerLocalError::AlreadyNegotiated, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/3ad27ee7cb31bf14975cd02bd68431e9876e2f76/litebox_broker_local/src/error.rs:16
  variant BrokerLocalError::IncompatibleNegotiation, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/3ad27ee7cb31bf14975cd02bd68431e9876e2f76/litebox_broker_local/src/error.rs:22
  variant BrokerLocalError::UnsupportedLocalVersion, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/3ad27ee7cb31bf14975cd02bd68431e9876e2f76/litebox_broker_local/src/error.rs:31
  variant BrokerLocalError::UnsupportedVersion, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/3ad27ee7cb31bf14975cd02bd68431e9876e2f76/litebox_broker_local/src/error.rs:40

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.48.0/src/lints/inherent_method_missing.ron

Failed in:
  BrokerLocal::new, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/3ad27ee7cb31bf14975cd02bd68431e9876e2f76/litebox_broker_local/src/lib.rs:38