docs(re): add reverse-engineering knowledge base + conventions

Establish docs/re/ as the spec-side of the clean-room:
- README: confidence tiers (HYPOTHESIS/PROBABLE/CONFIRMED), promotion
  requires NEW independent evidence, append-only evidence logs,
  demote-on-contradiction, and a clean-room firewall (describe behaviour +
  cite addresses; never paste decompiled code). Documents the toolchain
  (sylpheed.db + zq.py, xenia-rs probes, Wine-Canary oracle) and the
  join-by-guest-PC method with the VA-equality caveat.
- Function/structure templates + a seeded INDEX (9 already-reversed formats).
- First entry: texture-color-k8888 — CONFIRMED plain k_8_8_8_8 is linear
  UNORM (no sRGB), channel order still to be measured.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/re/_TEMPLATE.structure.md

@@ -0,0 +1,29 @@
+# `<structure / format name>`
+
+- **Confidence:** `HYPOTHESIS | PROBABLE | CONFIRMED`
+- **Parser in:** `crates/sylpheed-formats/src/…rs` — or *not yet*
+- **Seen in:** which pak / asset / memory region
+- **Related:** other RE entries, `[[memory-slug]]`
+
+## Layout
+```text
+offset  size  type   name        notes
+0x00    4     magic  "____"
+0x__    4     u32be  …
+…
+```
+Endianness, alignment, variable-length rules, how child/section sizes are derived.
+
+## Field semantics
+What each field *means* and its observed value range. Distinguish **confirmed** fields from
+**guessed** ones explicitly (a guessed field with a plausible value is still a guess).
+
+## Coverage / limits
+What fraction of real instances this decodes; which variants are deferred and why.
+
+## Evidence log (append-only; newest last)
+- `YYYY-MM-DD` — how established (forensic scan over N disc entries / round-trip test /
+  oracle comparison). → confidence `…`.
+
+## Open questions / what would raise confidence
+e.g. "colours unverified until compared against canary's framebuffer."