This pull request introduces several improvements and refactorings across the codebase, focusing on centralizing application subscriptions, enforcing greenfield development principles (no legacy support), improving code clarity and maintainability, and enhancing validation UI. The most significant change is the extraction and centralization of all Iced subscriptions into a dedicated module, making the codebase cleaner and easier to maintain. Additionally, there are updates to documentation and project policies to strictly prohibit legacy support, as well as minor bug fixes and UI enhancements.

Centralization and Refactoring of Application Subscriptions:

• Extracted all Iced application subscriptions from app/mod.rs into a new subscription module, providing a single point of management for event subscriptions and improving maintainability. The main App struct now delegates to this module. (crates/tss-gui/src/app/mod.rs, crates/tss-gui/src/app/subscription.rs) [1] [2] [3]

Greenfield Development and No Legacy Support Policy:

• Added detailed documentation in both CLAUDE.md and .claude/rules/00-deliberation.md explicitly forbidding any form of legacy support, including wrappers, backward compatibility, deprecation notices, migration code, and compatibility shims. The only acceptable approach is full rewrites. (CLAUDE.md, .claude/rules/00-deliberation.md) [1] [2]

Code Simplification and Idiomatic Rust:

• Refactored numerous pattern matches to use the let ... else idiom for early returns, simplifying control flow and improving code readability in handlers and utility functions. (crates/tss-gui/src/handler/domain_editor.rs, crates/tss-gui/src/handler/export.rs) [1] [2] [3] [4] [5] [6] [7]

Validation UI Enhancements:

• Improved the domain validation UI to properly support and display informational (Info) severity issues, including filtering, iconography, and color coding. (crates/tss-gui/src/view/domain_editor/validation.rs) [1] [2] [3] [4]

Dependency and Build System Updates:

• Added the encoding_rs crate as a workspace dependency in Cargo.toml. (Cargo.toml)
• Commented out the security audit job in the Rust CI workflow, possibly for performance or maintenance reasons. (.github/workflows/rust-ci.yml)

Bug Fixes:

• Fixed a bug in create_study_from_assignments by passing the SDTM context explicitly to the controlled terminology loader. (crates/tss-gui/src/app/util.rs, crates/tss-gui/src/service/study.rs) [1] [2]

• Fixes [Feat]: Add "not collected" reason to Define-XML output #118

• Fixes [Bug]: CT validation only shows first 5 invalid values #123

• Fixes [Bug]: Unknown constants silently return empty string #124

• Fixes [Bug]: Date validation accepts partial precision without warning #125

• Fixes [Feat]: Make CT versions discoverable from directory scan #126

• Fixes [Feat]: Validate Define-XML metadata version OID format #127

• Fixes [Feat]: Add range checks for numeric variables #128

• Fixes [Bug]: Polars schema inference only scans 100 rows #139

• Fixes [Bug]: UTF-16 BOM handling missing (Windows) #140

• Fixes [Bug]: Windows path length limit not checked #141

• Fixes [Feat]: Add file integrity checksum to project files #146

• Fixes [Feat]: Add validation for extensible codelists #247

• Fixes [Feat]: Add CT version consistency validation #246

• Fixes [Bug]: CT registry doesn't track which catalog is primary #249

• Fixes [Enhancement]: Adopt if-let chains (Rust 1.80+) #274

• Fixes [Enhancement]: Standardize Result handling patterns #275

• Fixes [Enhancement]: Improve subscription lifecycle management #276

• Fixes [Enhancement]: Adopt let-else pattern for cleaner early returns #279