docs: the 0.3.2 pre-release bookkeeping (changelog + readme ride notes)

- CHANGELOG: the 0.3.2 entry (alktunnels 0.4.1 -> 0.5.0, the
  correlation-gate release; patch, additive-only, no path change).
- README: the 0.3.2 version-history paragraph, same pattern.

Release machinery (tag + publish) deliberately deferred until the
doc-cleanup session lands.

README.md

@@ -255,6 +255,18 @@ to the bind-first adopt flow) and the alktunnels bump 0.4.0 → 0.4.1
 there is no change on this crate's paths; patch rather than minor
 because both dependency bumps are semver-compatible.
 
+0.3.2 rides the alktunnels bump 0.4.1 → 0.5.0 (the correlation-gate
+release — the forwarded op's serving half gains an establishment
+phase, `register_tunnel_forwarded_openable_with_establisher` +
+`ForwardedGate`: a stale/missing `listen` token fails the open as a
+typed `channel:open_failed` instead of success-then-silent-birth-
+teardown). Additive API only, no wire change, no alkcall bump
+(0.10.1 rides on); the composed accept stays on the base
+`register_tunnel_forwarded_openable` (kept byte-for-byte upstream),
+so there is no change on this crate's paths. Patch rather than minor:
+semver-compatible additive dependency bump, matching the 0.3.1
+precedent.
+
 ## Verification
 
 ```bash