Execute Todo

# Execute TODO

Work through every actionable item in `docs/TODO.md` sequentially without stopping for input.

## Process (repeat until the TODO list is empty or only deferred items remain)

1. **Read** `docs/TODO.md` and pick the next concrete, implementable item. Skip items that are explicitly complex/deferred (e.g. "ParasiteSubtype", "Door interaction", "Liberator lerp") unless they are the only items left.

2. **Investigate** — read all source files relevant to the item before writing any code. Understand the current state; never modify code you haven't read.

3. **Implement** the item:
   - Keep changes focused: one concern per system, no speculative abstractions.
   - Add `#[cfg(test)]` unit tests for any pure logic introduced.
   - Follow all rules in `CLAUDE.md` (no `cd`, no `rand::thread_rng()`, gate new systems with `run_if(in_state(GameState::Playing))` where appropriate, `LevelEntity` on level-scoped spawns, etc.).

4. **Build & test**:
   ```bash
   cargo check
   cargo check --features debug
   cargo test -p necrophage-core

Fix all errors and warnings before proceeding. Zero errors, zero warnings is the bar.

5. Remove the item from docs/TODO.md (delete the checkbox line). If a sub-item was only partially addressed, update the wording to reflect what remains.

6. Commit and push:

   git -C <project_dir> add -A
   git -C <project_dir> commit -m "<concise summary>\n\nCo-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>"
   git -C <project_dir> push origin master
   

7. Loop — go back to step 1 with the updated TODO.

Notes

• Tackle simpler, higher-value items before complex ones.
• Items in the MVP Vertical Slice checklist require a running game and cannot be automated — skip them.
• Items tagged as "complex" or "out of scope" in the TODO comments may be deferred; note them and move on.
• After finishing all feasible items, update docs/PRODUCT_PLAN.md and docs/IMPLEMENTATION_PLAN.md to reflect the new state, then do a final commit.