Bump version to 0.5.0; add Linux riscv64 release build (#394)

- release.yml: new `linux-riscv64` job ported from GridCraft. Cross-compiles
  wordcraft and wordcraft-cli on ubuntu-24.04 with riscv64 libs from
  ports.ubuntu.com (riscv64 variants of the Linux job's -dev packages),
  packages a tar.gz, and smoke-tests the CLI under QEMU. The draft-release
  job needs it, so its tar.gz is uploaded and covered by SHA256SUMS.
- packaging/linux/package.sh: CROSS_ARCH/CROSS_TARGET/CROSS_COMPILE/EMULATOR
  support (as in GridCraft).
- README and docs/releasing.md list the riscv64 tarball.

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

Cargo.lock

@@ -4998,7 +4998,7 @@ checksum = "1ebf944e87a7c253233ad6766e082e3cd714b5d03812acc24c318f549614536e"
 
 [[package]]
 name = "wordcraft"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "arboard",
  "eframe",
@@ -5019,7 +5019,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-cli"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "serde_json",
  "wordcraft-doc",
@@ -5031,11 +5031,11 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-control-key"
-version = "0.4.0"
+version = "0.5.0"
 
 [[package]]
 name = "wordcraft-doc"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "proptest",
  "serde",
@@ -5047,7 +5047,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-docbin"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "cfb",
  "log",
@@ -5060,7 +5060,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-docx"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "aes",
  "base64",
@@ -5082,7 +5082,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-engine"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "image",
  "js-sys",
@@ -5108,7 +5108,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-fonts"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "harfrust 0.13.3",
  "kurbo",
@@ -5119,7 +5119,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-formats"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "image",
  "log",
@@ -5132,14 +5132,14 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-geom"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "wordcraft-layout"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "js-sys",
  "log",
@@ -5156,7 +5156,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-mcp"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "log",
  "serde_json",
@@ -5168,7 +5168,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-metafile"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "kurbo",
  "thiserror 2.0.21",
@@ -5176,7 +5176,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-pdf"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "hayro-cmap",
  "hayro-interpret",
@@ -5196,7 +5196,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-proof"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "log",
  "miniz_oxide 0.8.9",
@@ -5205,7 +5205,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-render"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "image",
  "log",
@@ -5219,7 +5219,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-ui-egui"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "egui",
  "egui_kittest",
@@ -5241,7 +5241,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-web"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "eframe",
  "egui",
@@ -5259,7 +5259,7 @@ dependencies = [
 
 [[package]]
 name = "wordcraft-zotero"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "log",
  "proptest",
@@ -5361,7 +5361,7 @@ checksum = "9440ea3e5aeabb0ac63af70daf835274065238cdd0cec83418f417eae38bacee"
 
 [[package]]
 name = "xtask"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "serde_json",
 ]