docs(tier): add state diagram and transition rules

[emersonbusson]

Summary

Added a mermaid state diagram and comprehensive transition rules to the Tier enum rustdoc in cascade.rs.

Issue

N/A

Owner

IDENTIDADE

Labels

type:documentation area:core-crates-polish core-crates-polish

Commits

Commit	What was done	Why it was done	Details
e7bae5c	Added rustdoc	To document state transitions and triggers	Details Added Mermaid diagram

Validation

cargo clippy and cargo test pass.

Rollback trigger

Revert if docs build fails or diagram renders incorrectly.

RULES
MAIN_DIFF
FILES
INVARIANTS
COUNTERFACTUAL
RED_TEST
COVERAGE
REAL_PROOF
ROLLBACK
PR_BOUNDARY

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PR created automatically by Jules for task 15419095994983805554 started by @emersonbusson

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