Add conditional state transition spec

[enricopiovesan]

Governing Spec

• 053-conditional-state-transitions

Project Item

• Closes Spec: conditional state machine transitions based on capability output values #536

Validation

• cargo fmt --check
• cargo test -p traverse-registry
• bash scripts/ci/rust_checks.sh
• bash scripts/ci/repository_checks.sh
• BASE_SHA=origin/main bash scripts/ci/spec_alignment_check.sh /private/tmp/issue536-pr-body.md
• PATH=/Users/enricopiovesan/.cargo/bin:/opt/homebrew/opt/rustup/bin:$PATH bash scripts/ci/coverage_gate.sh
• python3 -m json.tool specs/governance/approved-specs.json
• git diff --check

Notes

• Adds the manifest schema and validation slice for conditional state-machine transitions.
• HTTP command dispatch, session execution, and state subscription behavior remain in follow-up Project tickets.
• Local sandboxed coverage failed only because loopback test servers could not bind ephemeral ports; the same coverage gate passed outside the sandbox.