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/alu/extswx.md

@@ -0,0 +1,120 @@
+# `extswx` — Extend Sign Word
+
+> **Category:** [Integer ALU](../categories/alu.md) · **Form:** [X](../forms/X.md) · **Opcode:** `0x7c0007b4`
+
+<!-- GENERATED: BEGIN -->
+
+## Assembler Mnemonics
+
+| Mnemonic | XML entry | Flags | Description |
+| --- | --- | --- | --- |
+| `extsw` | `extswx` | — | Extend Sign Word |
+| `extsw.` | `extswx` | Rc=1 | Extend Sign Word |
+
+## Syntax
+
+```asm
+extsw[Rc] [RA], [RS]
+```
+
+## Encoding
+
+### `extswx` — form `X`
+
+- **Opcode word:** `0x7c0007b4`
+- **Primary opcode (bits 0–5):** `31`
+- **Extended opcode:** `986`
+- **Synchronising:** no
+
+| Bits | Field | Meaning |
+| --- | --- | --- |
+| 0–5 | `OPCD` | primary opcode |
+| 6–10 | `RT/FRT/VRT` | destination |
+| 11–15 | `RA/FRA/VRA` | source A |
+| 16–20 | `RB/FRB/VRB` | source B |
+| 21–30 | `XO` | extended opcode (10 bits) |
+| 31 | `Rc` | record-form flag |
+
+## Operands
+
+| Field | Role | Description |
+| --- | --- | --- |
+| `RS` | extswx: read | Source GPR (alias for RD in some stores). |
+| `RA` | extswx: write | Source GPR (`r0`–`r31`). |
+| `CR` | extswx: write (conditional) | Condition-register update. When `Rc=1`, CR field 0 (or CR6 for vector compares, CR1 for FPU) is updated from the result. |
+
+## Register Effects
+
+### `extswx`
+
+- **Reads (always):** `RS`
+- **Reads (conditional):** _none_
+- **Writes (always):** `RA`
+- **Writes (conditional):** `CR`
+
+## Status-Register Effects
+
+- `extswx`: **CR0** ← signed-compare(result, 0) with `SO ← XER[SO]`, when `Rc=1`.
+
+## Operation (pseudocode)
+
+```
+RA <- EXTS_32_to_64((RS)[32:63])
+```
+
+## 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
+
+**`extswx`**
+- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="extswx"`](../../xenia-canary/tools/ppc-instructions.xml)
+- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_alu.cc:740`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_alu.cc#L740)
+- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:25`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L25)
+- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:852`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L852)
+- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:603-607`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L603-L607)
+<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
+
+```rust
+        PpcOpcode::extswx => {
+            ctx.gpr[instr.ra()] = ctx.gpr[instr.rs()] as i32 as i64 as u64;
+            if instr.rc_bit() { ctx.update_cr_signed(0, ctx.gpr[instr.ra()] as i64); }
+            ctx.pc += 4;
+        }
+```
+</details>
+
+<!-- GENERATED: END -->
+
+## Special Cases & Edge Conditions
+
+- **Sign-extends the low 32 bits of `RS` to 64 bits.** Bit 32 (sign bit of the word) is replicated through bits 0–31 of `RA`.
+- **Used heavily in 32-to-64-bit promotion.** Most Xbox 360 ABI parameters are 32-bit; promoting a 32-bit `int` to a 64-bit GPR requires this instruction. Many functions emit it on entry to canonicalise their argument registers.
+- **`Rc=1` CR0 update is correctly 64-bit.** [`interpreter.rs:399`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L399) uses `as i64` (no truncation) — one of the few xenia-rs sites where the spec width is honoured. The signed compare in CR0 reflects the full sign-extended value.
+- **Operand convention** is the X-form one (`RA` destination, `RS` source).
+- **No `XER` side effects.**
+- **`RB` field unused.**
+- **Aliasing is fine.** `extsw r3, r3` is the canonical "sign-extend in place" idiom.
+- **Distinct from `srawi RA, RS, 31`**, which produces the *sign mask* (`-1` if negative else `0`) rather than the sign-extended value.
+
+## Related Instructions
+
+- [`extsbx`](extsbx.md), [`extshx`](extshx.md) — narrower sign extensions.
+- [`srawix`](srawix.md) — to derive a sign mask instead.
+- [`rldiclx`](rldiclx.md) — to *zero*-extend the low 32 bits.
+- `lwa` / `lwax` (memory ops) — combined load-and-sign-extend; lives outside this set.
+
+## IBM Reference
+
+- [AIX 7.3 — `extsw` (Extend Sign Word)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-extsw-extend-sign-word-instruction)