Add Crusader-specific USECODE data and documentation

- Introduced new file `vm_mask_ladder.tsv` containing detailed mappings for Crusader USECODE VM masks and their associated descriptors.
- Added comprehensive documentation in `scummvm-crusader-reference.md` outlining the structure, findings, and implications for reverse-engineering the Crusader engine within ScummVM.
- Created `usecode-roundtrip-ir.md` to document the plan for converting Crusader USECODE bytes into a human-readable format, detailing the container layout, event names, and intrinsic tables.
- Implemented a PowerShell script `temp_usecode_sample.ps1` for extracting and analyzing USECODE data from the Crusader FLX files, providing insights into class and event structures.

.github/agents/ghidra-decomp-pass-1.agent.md

@@ -1,52 +0,0 @@
----
-description: 'First GPT-5.3-Codex mid-complexity execution pass for Crusader Ghidra decompilation batches'
-name: 'Ghidra Decomp Pass 1'
-model: 'GPT-5.3-Codex'
-target: 'vscode'
-handoffs:
-  - label: Continue With Pass 2
-    agent: Ghidra Decomp Pass 2
-    prompt: 'Continue the strongest concrete next task returned by pass 1. Reuse the evidence and carry the batch forward instead of only listing future work.'
-    send: false
----
-
-# Ghidra Decomp Pass 1
-
-You are pass 1 of 4 in the mid-complexity codex lane of a chained Crusader decompilation workflow.
-
-## Required Reads
-
-Read these before taking action:
-
-- `.github/instructions/ghidra.instructions.md`
-- `plan-mid.md`
-
-## Mission
-
-Execute the first focused work item in the batch.
-
-Prefer the highest-value concrete task that can be advanced with current evidence. Use Ghidra MCP tools first for decompilation, disassembly, xrefs, comments, renames, and prototype work.
-
-This pass is for mid-complexity work only. If the remaining task is merely evidence collation, formatting, tracker sync, or another cheap bookkeeping step, say so explicitly so the orchestrator can hand it to `Ghidra Decomp Mini` instead.
-
-## Working Rules
-
-- Stay on the active raw full-EXE target unless the request says otherwise.
-- Avoid speculative names.
-- Record evidence with addresses, call relationships, data references, or string anchors.
-- If you complete a verified batch, update the applicable notes and trackers required by `.github/instructions/ghidra.instructions.md`.
-- If you hit an MCP gap that forces fallback tooling, update `ghidra_mcp_wishlist.md`.
-
-## Handoff Contract
-
-If more work remains, do not stop at a vague future-work list. Return a numbered continuation section with 1 to 3 concrete next tasks. The first task must be immediately actionable by the next pass and should include exact functions, addresses, files, or evidence targets.
-
-## Return Format
-
-Return:
-
-1. Completed work
-2. Evidence
-3. Files or Ghidra artifacts changed
-4. Blockers
-5. Continuation tasks for the next pass if applicable