(engine) Prepare v0.26.0 release

[tcballard]

Outcome

Prepares v0.26.0 as the minor release for deterministic decision-to-code enforcement.

Changes

• bumps the Rust workspace from 0.25.1 to 0.26.0
• updates the exact decided dependency on asdecided-core
• refreshes all three workspace package entries in Cargo.lock

Release capability

The release carries the merged Sentry stack from #395–#397:

• decided sentry and decided gate --code
• deterministic pattern and import constraints
• native blocking CI and SARIF output
• 20/121 live decisions explicitly classified (16.53% corpus adoption)
• 20/20 eligible decisions constrained (100% eligible coverage)
• 46 active deterministic rules
• no embeddings, model call, network service, or LLM judge

Verification

• cargo metadata --locked --no-deps --format-version 1
• cargo test --workspace --locked
• full-tree decided sentry: pass, 0 findings