Add calibration evidence registration gate

[rsasaki0109]

What changed

• Add CalibrationEvidenceState with source-bound clock quality and front/rear frame-graph validation.
• Add the feature-gated rosbag2_calibration_evidence example with strict JSON evidence documents, external JSON/HTML/manifest receipts, and fail-closed exit status 2.
• Let rosbag2_mission_cockpit consume an optional calibration-evidence receipt and surface its blockers/artifact checksum without hiding publish/partition inspection.
• Update the roadmap, real-data acceptance contract, changelog, and implementation note.

Why

The canonical bag has no clock, TF, or extrinsic artifacts. This slice creates the real registration contract without fabricating calibration values or applying unverified transforms.

External evidence

• Canonical no-artifact evidence receipt: /media/sasaki/aiueo/spatialrust-results/v1-3/145j-calibration-evidence-v2/
• Wrong-SHA probe: /media/sasaki/aiueo/spatialrust-results/v1-3/145j-calibration-evidence-validation-probe-v1/
• Mission Cockpit integration: /media/sasaki/aiueo/spatialrust-results/v1-3/145j-mission-cockpit-145jb-v1/

Checks

• cargo fmt --all -- --check
• cargo test --workspace
• cargo clippy --workspace --all-targets -- -D warnings
• cargo clippy --workspace --all-features --lib -- -D warnings
• cargo test --workspace --all-features --no-run
• targeted browser JavaScript syntax checks