app decomposition, package moves, and ripple effect tuning

[FelineStateMachine]

Summary

This branch is the full feat/app-decomposition stack, not just the final Ripple Effect follow-up. It reorganizes built-in package layout, decomposes more of the Bubble Tea app shell into screen-local models, and updates Ripple Effect generation/tests.

Diff Overview

• 304 files changed, 1002 insertions, 854 deletions
• Most of the file count is mechanical package moves and import rewrites
• Behavioral changes are concentrated in app/, registry/, gameentry/, and games/rippleeffect/

What Changed

1. Package layout cleanup

• Moved built-in game implementations from top-level packages into games/*
• Moved print/export runtime packages into export/*
• Updated imports across app, cmd, registry, tests, and adapters to match the new package map
• Preserved package behavior for most moved files; the majority of these changes are renames with minimal code edits

Examples:

• fillomino -> games/fillomino
• rippleeffect -> games/rippleeffect
• pdfexport -> export/pdf
• packexport -> export/pack
• builtinprint -> export/builtinprint

2. App/screen decomposition

• Continued the Bubble Tea refactor by moving more view-specific behavior into screen-local models instead of keeping everything on the root app model
• Reworked export flow state so the export form owns its UI/input state while the surrounding screen owns job lifecycle concerns
• Simplified screen navigation and reduced duplicated root-level handler logic in the app shell
• Updated app tests to match the decomposed screen structure and navigation behavior

Primary files:

• app/export.go
• app/model.go
• app/screen_core.go
• app/screen_navigation.go
• app/update.go
• app/view.go

3. Registry/runtime wiring

• Updated the built-in runtime registry to import from the new games/* package locations
• Kept catalog, registry, and gameentry responsibilities aligned with the repo package map
• Refreshed architecture assertions/tests to reflect the new boundaries

Primary files:

• registry/registry.go
• gameentry/gameentry.go
• architecture_test.go

4. Ripple Effect difficulty and generator work

• Expanded the games/rippleeffect changes beyond a pure rename
• Tuned mode/generation profile behavior for larger sparse boards
• Added a substantial Ripple Effect test suite covering geometry, validation, solver uniqueness, import/export, rendering, and sampled generation invariants
• Fixed a generator correctness issue where singleton normalization could return cages larger than Mode.MaxCage
• Trimmed the Expert sampled test budget so full CI completes reliably while still checking the relevant post-generation invariants

Primary files:

• games/rippleeffect/gamemode.go
• games/rippleeffect/generator.go
• games/rippleeffect/rippleeffect_test.go
• games/rippleeffect/README.md

Why

• Make the repo package structure line up with the intended architecture (games, export, registry, gameentry)
• Reduce coupling in the app shell by keeping screen state closer to the screen that owns it
• Strengthen Ripple Effect generation/validation while keeping CI practical

Validation

• just fmt
• just lint
• just test