Export: headless CLI mode for the GGPK exporter (one-command patch export)

[jay9297]

Goal

Make the GGPK data exporter runnable as one CLI command instead of a GUI-only flow, so a patch export becomes <command> --ggpk <path> --run-all on the maintainer's machine. This is the prerequisite for ever automating exports further.

⚠️ Constraint for AI agents

The exporter needs a local PoE2 install and the Windows-only bun_extract_file.exe — neither exists in CI or agent sessions. An agent CAN do the refactor and verify the new entry point loads, parses arguments, and fails gracefully without game files; final verification against a real GGPK must be done by a human (@jay9297). Say so explicitly in the PR.

Background (read first)

• Read CLAUDE.md and CONTRIBUTING.md (exporter setup section, ~lines 246–287).
• Current flow: src/Export/Launch.lua boots a SimpleGraphic GUI ("Dat View", src/Export/Main.lua); the user clicks "Edit Sources…" to set the GGPK path, then "Run All" to execute the 16 scripts in src/Export/Scripts/ (statdesc.lua always first — see Main.lua:186-198).
• The repo already has the pattern for running GUI code headlessly: src/HeadlessWrapper.lua stubs all rendering callbacks so the main app runs under plain LuaJIT (it's what the test suite boots through). The exporter needs the same treatment.

What to build

1. Audit GUI coupling in the export path. Grep src/Export/Main.lua, src/Export/Classes/*.lua, and src/Export/Scripts/*.lua for rendering/UI calls (Draw*, SetDrawColor, controls, IsKeyDown, popup/dialog functions). The export scripts are mostly pure data processing; the coupling is concentrated in Main.lua (script list UI, console rendering) and possibly progress output.

2. Create src/Export/HeadlessExport.lua modeled on src/HeadlessWrapper.lua:

   • Stubs the SimpleGraphic callbacks exactly as HeadlessWrapper.lua does (copy its stub set; print ConPrintf output to stdout).
   • Accepts CLI args: --ggpk <path-to-Content.ggpk-or-game-dir> (required), --script <name> (repeatable), --run-all.
   • Initializes the same state Main.lua:Init() builds (GGPK reader via src/Export/Classes/GGPKData.lua, DAT specs from src/Export/spec.lua), without constructing UI controls. Refactor Main.lua so the logic (source setup, script execution order incl. statdesc-first, error collection) lives in functions callable from both the GUI and the headless entry — do not duplicate the logic.
   • Exit code 0 only if all requested scripts ran without errors; print per-script pass/fail summary.

3. Document it in CONTRIBUTING.md next to the existing GUI instructions: luajit src/Export/HeadlessExport.lua --ggpk "C:\...\Content.ggpk" --run-all (note it still requires the ggpk/ extractor binaries).

Acceptance criteria

• luajit src/Export/HeadlessExport.lua (no args) prints usage and exits non-zero — verifiable in the test container.
• With a bogus --ggpk /nonexistent it fails with a clear error, not a nil-reference crash — verifiable in the test container.
• The GUI exporter still works: no behavior change to Launch.lua flow beyond the refactor (this is hard to test headlessly — keep the refactor mechanical: extract functions, don't rewrite them).
• Full test suite passes: docker compose run --rm busted-tests (exporter code isn't covered by tests, but the suite guards against accidental damage elsewhere).
• PR explicitly lists what was verified headlessly vs. what needs the maintainer's real-GGPK run.

Out of scope

• Cross-platform extraction (replacing bun_extract_file.exe).
• Scheduled/CI exports.
• Changing what any export script outputs.