Centralize the complete benchmark harness in v3

[Krastanov]

Summary

• move measurement scheduling, scenario execution, validation, and summarization into the action repository
• infer package identity and relative path dependencies from each checkout
• leave consumers with only their package-specific scenarios
• provide a deterministic v3.0.0 local tool bundle with checksums
• fix the action to Julia 1.12.6 and pin all nested actions by commit

Released as v3.0.0. Both v3 tags resolve to merge commit a8afb46.

Checks

• real fixture comparison in resolved and reused environment modes
• generic relative path dependency normalization in both modes
• exact result schema, row counts, metadata, and Markdown checks
• deterministic release archives under umask 0022 and 0077
• shell syntax, Julia syntax, diff checks, CodeQL, and independent review
• extracted release-bundle comparison against the path-dependency fixture
• released-action integrations in QuantumClifford, QuantumSavory, and QuantumOpticsBase