Web: size-optimised wasm profile (27.0 → 18.1 MB); bump to 0.3.1 (#109)

The 0.3.0 web release failed packaging/web/package.sh's 24 MiB gate: the wasm grew from
22.2 MB (0.2.0) to 27.0 MB once the plugin sandbox (wasmi + wasmparser, #101) and the
collaboration crates (#103-#105) joined the browser build, which still used the desktop
`release` profile (opt-level 3, thin LTO, 4 codegen units).

- Cargo.toml: new `web-release` profile (inherits release; opt-level "s", fat LTO, one codegen
  unit, no debug info, stripped). opt-level "z" measured 16.9 MB; "s" keeps render speed.
- apps/figcraft-web/index.html: build with that profile, and pass the wasm features rustc emits
  (bulk memory etc.) to wasm-opt, which otherwise rejects the size-optimised module.
- Version 0.3.0 -> 0.3.1. docs/releasing.md: the web profile and size history.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.toml

@@ -6,7 +6,7 @@ exclude = ["plugins"]
 # default-members = ["crates/*", "apps/figcraft", "apps/figcraft-cli", "xtask"]
 
 [workspace.package]
-version = "0.3.0"
+version = "0.3.1"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.95"
@@ -96,3 +96,15 @@ opt-level = 1
 [profile.release]
 lto = "thin"
 codegen-units = 4
+
+# The browser build only (apps/figcraft-web/index.html: data-cargo-profile). Optimised for size:
+# packaging/web/package.sh fails a .wasm over 24 MiB (Cloudflare's per-file cap is 25 MiB).
+# wasm32-unknown-unknown always aborts on panic, so panic = "abort" changes nothing there.
+[profile.web-release]
+inherits = "release"
+opt-level = "s"
+lto = "fat"
+codegen-units = 1
+debug = false
+strip = true
+panic = "abort"