docs: development workflow + phase-by-phase audit

Adds mandatory decompile→verify→port workflow to CLAUDE.md:
- DECOMPILE FIRST before writing ANY AC-specific code
- Cross-reference against ACE/ACME (interpretation aids)
- Write pseudocode before porting (catches misinterpretations)
- Port faithfully — don't "improve" the retail code
- Conformance test the critical paths
- Integrate surgically — minimum changes to working code
- Phase completion checklist with decompiled-reference citations

Phase audit (docs/audit/2026-04-13-phase-audit.md) reviews all
shipped phases:
- 53% verified (decompiled/ACME conformance)
- 34% from good references (ACE/ACViewer/holtburger)
- 5% guessed (lighting, indoor transitions)
- 8% not AC-specific (streaming, culling)

Key gaps identified:
1. Lighting uses guessed sun direction — should use decompiled AdjustPlanes
2. Indoor transitions disabled — needs decompiled CEnvCell port
3. SceneryGenerator LCG not verified against decompiled code
4. CreateObject parser incomplete
5. Movement messages missing sequence counters

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -64,6 +64,79 @@ a phase just landed, and move to the next todo item.
 always yes — keep going.** The single exception is visual verification;
 otherwise, act.
 
+## Development workflow: decompile → verify → port
+
+**This is the mandatory workflow for implementing ANY AC-specific behavior.**
+The triangle-boundary Z bug cost 5 failed fix attempts from guessing.
+The animation frame-swap bug cost 4 failed attempts. Every time we
+checked the decompiled code first, we got it right on the first try.
+
+### For each new feature or bug fix:
+
+1. **DECOMPILE FIRST.** Before writing any AC-specific code, find the
+   matching function in the decompiled client (`docs/research/decompiled/`)
+   or decompile a new region using `tools/decompile_acclient.py`. Use
+   the function map at `docs/research/acclient_function_map.md` to find
+   known functions. If the function isn't mapped yet, search by
+   characteristic constants (motion commands, magic numbers, string
+   literals).
+
+2. **CROSS-REFERENCE.** Check the decompiled code against ACE's C# port
+   (`references/ACE/Source/ACE.Server/Physics/`) and ACME's
+   `ClientReference.cs`. The decompiled code is ground truth; ACE and
+   ACME are interpretation aids. If they disagree, the decompiled code
+   wins.
+
+3. **WRITE PSEUDOCODE.** Translate the decompiled C into readable
+   pseudocode before porting to C#. Save it in
+   `docs/research/*_pseudocode.md` for future reference. This step
+   catches misinterpretations before they become bugs.
+
+4. **PORT FAITHFULLY.** Translate the pseudocode to C# line-by-line.
+   Use the same variable names, the same control flow, the same boundary
+   conditions. Do not "improve" or "simplify" the algorithm — the retail
+   client's code works; our job is to match it.
+
+5. **CONFORMANCE TEST.** Write tests that verify our port matches the
+   decompiled behavior. Use golden values from the decompiled code or
+   from ACME's conformance tests. If the function touches terrain, port
+   the 4M-cell sweep from `TerrainConformanceTests.cs`.
+
+6. **INTEGRATE SURGICALLY.** When wiring ported code into the renderer
+   or game loop, change the MINIMUM necessary. Keep existing working
+   transform pipelines, only replace the specific computation. The
+   animation sequencer integration proved this: replacing the slerp
+   source was safe; replacing the entire transform composition broke
+   everything.
+
+### What NOT to do:
+
+- **Do not guess** at AC-specific algorithms, formulas, constants, wire
+  formats, or coordinate conventions. Ever.
+- **Do not "fix" the decompiled code.** If the retail client does
+  something that looks wrong, it's probably right. Verify before
+  changing.
+- **Do not skip the pseudocode step.** The frame-swap bug was caused by
+  misreading the decompiled C directly into C# without an intermediate
+  translation.
+- **Do not integrate via subagent** unless the subagent has the full
+  context of the existing code it's modifying. The first animation
+  sequencer integration was done by a subagent that didn't understand
+  the transform pipeline — it broke everything.
+
+### Phase completion checklist:
+
+Before marking any phase as done:
+
+- [ ] Every AC-specific algorithm has a decompiled reference cited in
+      comments (function address + chunk file)
+- [ ] Conformance tests exist for the critical paths
+- [ ] The code was cross-referenced against at least 2 reference repos
+- [ ] `dotnet build` green, `dotnet test` green
+- [ ] Visual verification by the user (if applicable)
+- [ ] Roadmap updated
+- [ ] Memory updated if there's a durable lesson
+
 ## Subagent policy
 
 Subagents are the primary tool for saving parent-context and keeping one