Integrate Herdr 0.7.5 and prepare Tether v0.4.0

[moneycaringcoder]

Summary

• prepare the documented Tether v0.4.0 release surface and schema migrations
• add Herdr 0.7.5 CI/live-smoke coverage and use session-modal plugin popups when supported
• add explicit validated Herdr agent-kind hints for local and SSH-backed durable workloads
• add opt-in orchestration-group views in Herdr's native Agents sidebar, with persisted startup/live-handoff restoration and reversible cleanup
• retain Herdr 0.7.3 compatibility for the ordinary Tether and Observer workflows

Compatibility

The manifest minimum remains Herdr 0.7.3. Its parser ignores the newer [[startup]] table, popup placement remains overlay on 0.7.3, and metadata-token reporting is version-gated to 0.7.5. Agent sidebar view actions fail closed and restore their prior preference when the 0.7.5 API is unavailable.

Verification

• cargo test --locked --all-targets --all-features — 360 passed
• python3 -m unittest discover -s tools -p 'test_*.py' — 78 passed
• python3 tools/check_docs.py
• python3 tools/check_release.py --tag v0.4.0
• python3 tools/check_package.py --allow-dirty — 52 packaged files
• python3 tools/check_public_contracts.py --archive target/package/herdr-tether-0.4.0.crate --binary target/release/herdr-tether — 23 examples
• official Herdr 0.7.3 live product smoke — four consecutive complete runs after the final harness ordering fix
• official Herdr 0.7.5 live product smoke — four consecutive complete runs after the final harness ordering fix
• real Herdr 0.7.5 prototype — two Tether-backed Codex panes recognized through explicit hints; source-owned group view accepted; both panes accepted bounded tether_group metadata tokens

CI feedback addressed

The first workflow run found two release-harness issues: CI still checked v0.3.0, and a deliberate failed-create scenario could leave a recoverable pending record ahead of the external-session fixture on slower Linux runners. The follow-up commit checks v0.4.0 and runs the external attach contract before the isolated failure scenario. Both Herdr versions then passed three additional stress runs locally.