refactor(codegen): extract lifecycle/loop.zig from main_zig.zig (#183 step 8a)

[apotema]

Summary

Step 8a of the #183 refactor plan. Moves buildSetupCode (raylib/sdl/bgfx/wgpu loop-backend setup) and buildGuiDrawCode out of src/main_zig.zig into a dedicated src/codegen/lifecycle/loop.zig (235 lines). Re-exported from main_zig.zig so the orchestrator's buildSetupCode(...) / buildGuiDrawCode(...) call sites stay unchanged.

HIGH-risk extraction per the plan -- preserves call order across writeImageBackendWiring, writeAudioBackendWiring, writeFontBackendWiring, and emitResourceLoad. Verified bit-identical across all 8 working bundled examples (raylib, sokol, null, plugin-controllers, flows-smoke, asset-streaming-smoke, bgfx, wgpu). sokol_imgui still soft-fails because the labelle-imgui sibling repo is absent locally, same as on origin/main.

• main_zig.zig: 3817 -> 3628 lines (-189)
• src/codegen/lifecycle/loop.zig: 235 lines

Helpers reached back via main_zig.zig

On this branch the helpers consumed by buildSetupCode (writeImageBackendWiring, writeAudioBackendWiring, writeFontBackendWiring, emitResourceLoad, LoadStyle) are still inline in main_zig.zig -- they're pubified here so the new module can reach them. When the parallel blocks/asset_wiring.zig (#197) + blocks/resource_loader.zig (#199) cuts land, lifecycle/loop.zig's imports flip to those new modules and the pub markers in main_zig.zig retire alongside the moved bodies.

Test plan

• zig build -- clean
• zig build test -- 506/510 passed (4 skipped), unchanged from baseline
• scripts/gen_all_examples.sh before/after -- every generated main.zig byte-identical (only flow_catalog.json's generated_at timestamp differs, as documented in the plan)
• No --force push, no logic edits, pure cut + import

Builds on: #202 (umbrella branch feat/183-split-main-zig).
Refs: #183.

Co-authored-by: Claude Opus 4.7 (1M context) noreply@anthropic.com

[gemini-code-assist]

Code Review

This pull request extracts the loop-lifecycle code builders (buildSetupCode and buildGuiDrawCode) from src/main_zig.zig into a new dedicated module src/codegen/lifecycle/loop.zig as part of the #183 refactoring plan. To maintain backward compatibility and preserve existing call sites, these functions are re-exported from src/main_zig.zig. Additionally, several internal helpers in src/main_zig.zig (such as writeImageBackendWiring, LoadStyle, and emitResourceLoad) have been made public so they can be accessed by the new module. I have no feedback to provide as there are no review comments and the refactoring is clean and well-documented.

[cursor]

PR Summary

Medium Risk
Touches ordering-sensitive generated startup/GUI code for all loop backends, but the change is a verified byte-identical cut with no behavioral edits.

Overview
Step 8a of the #183 main_zig.zig split moves loop-backend lifecycle codegen into src/codegen/lifecycle/loop.zig: buildSetupCode (raylib/sdl/bgfx/wgpu setup: GUI init, asset wiring, runner, embedded resources/prefabs/scenes, plugins) and buildGuiDrawCode (GUI frame draw block). The bodies are a pure move—no logic edits—with the same helper call order as before.

main_zig.zig drops the inline implementations (~189 lines), imports lifecycle_loop, and re-exports both builders so generateMainZigFromTemplate still calls them unchanged. loop.zig reaches write*BackendWiring, emitResourceLoad, and pathToIdent via main_zig / scan (same pattern as callback.zig for sokol/wasm).

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