chore: add migration/ bundle for cross-machine setup

Bundles state that lives OUTSIDE the xenia-rs repo so a fresh clone on
another machine can be brought up to identical configuration via
migration/setup.sh:

  - claude-memory/             ~/.claude/projects/-home-fabi-RE-Project-Sylpheed/memory/
                               (103 files, 1.1 MB - MEMORY.md + every
                                project_xenia_rs_*.md from audits
                                addis_signext through audit-058)
  - project-root/dot-claude/   <project-root>/.claude/settings.json
                               (Stop hook + permissions)
  - project-root/ppc-manual/   <project-root>/ppc-manual/
                               (PowerPC reference docs, 397 files, 3.7 MB)
  - project-root/run-canary.sh <project-root>/run-canary.sh
  - README.md                  Human-readable setup checklist
  - setup.sh                   Idempotent installer (also reclones
                               xenia-canary at pinned HEAD 6de80dffe)
  - MANIFEST.md                Per-file mapping + per-file-not-bundled
                               restoration recipe

Excluded from bundle (not shippable via git):
  - Sylpheed ISO (7.8 GB; copyright; manual copy required)
  - sylpheed.db (395 MB; regenerable from XEX via analysis tooling)
  - target/ build artifacts (rebuild on target)
  - audit-runs probe firehoses (.log/.stdout/.stderr ~11 GB; rerun if needed)
  - audit-runs memory dumps (.bin ~4.5 GB; rerun audit-026/027/029 if needed)
  - xenia-canary checkout (setup.sh reclones from
    git.mc02.dev/fabi/Xenia-Canary.git at HEAD 6de80dffe)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

migration/project-root/ppc-manual/control/mtvscr.md

@@ -0,0 +1,125 @@
+# `mtvscr` — Move to VSCR
+
+> **Category:** [Control / CR / SPR](../categories/control.md) · **Form:** [VX](../forms/VX.md) · **Opcode:** `0x10000644`
+
+<!-- GENERATED: BEGIN -->
+
+## Assembler Mnemonics
+
+| Mnemonic | XML entry | Flags | Description |
+| --- | --- | --- | --- |
+| `mtvscr` | `mtvscr` | — | Move to VSCR |
+
+## Syntax
+
+```asm
+(no disassembly template)
+```
+
+## Encoding
+
+### `mtvscr` — form `VX`
+
+- **Opcode word:** `0x10000644`
+- **Primary opcode (bits 0–5):** `4`
+- **Extended opcode:** `1604`
+- **Synchronising:** no
+
+| Bits | Field | Meaning |
+| --- | --- | --- |
+| 0–5 | `OPCD` | primary opcode (4) |
+| 6–10 | `VRT/VD` | destination vector register |
+| 11–15 | `VRA/VA` | source A vector register |
+| 16–20 | `VRB/VB` | source B vector register |
+| 21–31 | `XO` | extended opcode (11 bits) |
+
+## Operands
+
+| Field | Role | Description |
+| --- | --- | --- |
+| `VB` | mtvscr: read | Source B vector register. |
+| `VSCR` | mtvscr: write | Vector Status and Control Register (NJ/SAT bits). |
+
+## Register Effects
+
+### `mtvscr`
+
+- **Reads (always):** `VB`
+- **Reads (conditional):** _none_
+- **Writes (always):** `VSCR`
+- **Writes (conditional):** _none_
+
+## Status-Register Effects
+
+- `mtvscr`: **VSCR[SAT]** may be stickied on saturating vector operations.
+
+## Operation (pseudocode)
+
+```
+; Pseudocode derives directly from the xenia-rs interpreter
+; arm (see Implementation References). Operation semantics:
+;   - Read source operands from the fields listed under Operands.
+;   - Apply the arithmetic / logical / memory action described
+;     in the Description field above.
+;   - Write results to the destination register(s); update any
+;     status bits enumerated under Status-Register Effects.
+; Consult the IBM AIX reference link under IBM Reference for
+; canonical PPC-style pseudocode where xenia's expression is
+; terse.
+```
+
+## C Translation Example
+
+```c
+/* C translation: the xenia-rs interpreter arm below in           */
+/* Implementation References is the authoritative semantic        */
+/* snapshot. Translate it line-by-line:                            */
+/*   - ctx.gpr[N]  -> r[N]       (or f[]/v[] for FPRs/VRs)        */
+/*   - mem.read_u*/write_u* -> mem_read_u*_be / mem_write_u*_be   */
+/*   - ctx.update_cr_signed(fld, v) -> update_cr_signed(fld, v)   */
+/*   - ctx.xer_ca / xer_ov / xer_so -> xer.CA / xer.OV / xer.SO   */
+/* The Register Effects and Status-Register Effects tables above  */
+/* enumerate every side effect a faithful translation must emit.  */
+```
+
+## Implementation References
+
+**`mtvscr`**
+- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="mtvscr"`](../../xenia-canary/tools/ppc-instructions.xml)
+- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_altivec.cc:310`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_altivec.cc#L310)
+- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:55`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L55)
+- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:542`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L542)
+- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:2514-2517`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L2514-L2517)
+<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
+
+```rust
+        PpcOpcode::mtvscr => {
+            ctx.vscr = ctx.vr[instr.rb()];
+            ctx.pc += 4;
+        }
+```
+</details>
+
+<!-- GENERATED: END -->
+
+## Special Cases & Edge Conditions
+
+- **Operation.** Reads the **low 32 bits of the rightmost word** of `VB` (bytes 12..15 in big-endian) and stores them into VSCR. Other bits of `VB` are ignored.
+- **Bits actually significant.** Of the 32 source bits, only **NJ (bit 16)** and **SAT (bit 31)** are architecturally meaningful on the Xenon. All other bits should be written as zero; behaviour for non-zero values is implementation-defined.
+- **Clearing SAT.** The dominant use is `mtvscr vN` with `vN` zeroed via `vxor vN, vN, vN`, which writes VSCR=0 and thereby clears the sticky SAT bit before a fresh batch of saturating vector ops.
+- **Setting NJ.** Switching to/from "Java mode" (`NJ=0`, full IEEE denormal handling) versus "Non-Java mode" (`NJ=1`, flush-to-zero) is the other meaningful use. Game audio / DSP code occasionally toggles this to match a precise IEEE expectation.
+- **xenia simplification.** xenia-rs stores VSCR identically to a vector register and copies the source straight in: `ctx.vscr = ctx.vr[VB]`. Subsequent xenia AltiVec ops do consult `VSCR[SAT]` for sticky updates, so the architecturally-relevant behaviour is preserved. NJ's flush-to-zero semantics are honoured by xenia's vector denormal paths.
+- **Not synchronising.** PowerISA does not require `isync` after `mtvscr`, but library code occasionally pairs them as a defensive measure.
+
+## Related Instructions
+
+- [`mfvscr`](mfvscr.md) — read VSCR into a vector register (the inverse).
+- AltiVec saturating ops (`vaddubs`, `vsubuhs`, …) — primary writers of `VSCR[SAT]`; `mtvscr` is the only way to clear it.
+- [`mtspr`](mtspr.md) — for non-vector control registers; VSCR has its own opcode.
+
+`mtvscr` has no simplified mnemonics.
+
+## IBM Reference
+
+- [AIX 7.3 — `mtvscr` (Move to VSCR)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-mtvscr-move-vector-status-control-register-instruction)
+- PowerISA v2.07B, Book I §6.6 — VSCR layout, SAT / NJ semantics.