feat(update): SHA-256 verification + reject paths containing '%'

GitHub's Releases API exposes a `digest: "sha256:..."` field on every
asset since 2024. We now parse it, hash the downloaded bytes locally,
and abort with ChecksumMismatch if they disagree. Releases that predate
the field (none currently exist for this repo) skip verification rather
than fail, so v0.1.0 / v0.1.1 / v0.1.2 still update normally.

cmd.exe expands `%var%` even inside double-quoted arguments, which
would let a path like `C:\Users\%PATHEXT%\bubble.exe` substitute the
expansion. Real Windows paths with `%` are vanishingly rare, so we
fail fast with UnsafePath rather than ship a bespoke cmd-escape
implementation.

Bumps version to 0.1.3.

Cargo.lock

@@ -44,6 +44,15 @@ version = "2.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c4512299f36f043ab09a583e57bceb5a5aab7a73db1805848e8fef3c9e8c78b3"
 
+[[package]]
+name = "block-buffer"
+version = "0.10.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3078c7629b62d3f0439517fa394996acacc5cbc91c5a20d8c658e77abd503a71"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "bytemuck"
 version = "1.25.0"
@@ -68,7 +77,7 @@ checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
 [[package]]
 name = "claude-code-usage-bubble"
-version = "0.1.2"
+version = "0.1.3"
 dependencies = [
  "dirs",
  "embed-resource",
@@ -76,6 +85,7 @@ dependencies = [
  "native-tls",
  "serde",
  "serde_json",
+ "sha2",
  "simplelog",
  "thiserror",
  "tiny-skia",
@@ -100,6 +110,15 @@ version = "0.8.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b"
 
+[[package]]
+name = "cpufeatures"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59ed5838eebb26a2bb2e58f6d5b5316989ae9d08bab10e0e6d103e656d1b0280"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "crc32fast"
 version = "1.5.0"
@@ -109,6 +128,16 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "crypto-common"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78c8292055d1c1df0cce5d180393dc8cce0abec0a7102adb6c7b1eef6016d60a"
+dependencies = [
+ "generic-array",
+ "typenum",
+]
+
 [[package]]
 name = "deranged"
 version = "0.5.8"
@@ -118,6 +147,16 @@ dependencies = [
  "powerfmt",
 ]
 
+[[package]]
+name = "digest"
+version = "0.10.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
+dependencies = [
+ "block-buffer",
+ "crypto-common",
+]
+
 [[package]]
 name = "dirs"
 version = "6.0.0"
@@ -241,6 +280,16 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "generic-array"
+version = "0.14.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85649ca51fd72272d7821adaf274ad91c288277713d9c18820d8499a7ff69e9a"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -761,6 +810,17 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "sha2"
+version = "0.10.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a7507d819769d01a365ab707794a4084392c824f54a7a6a7862f8c3d0892b283"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest",
+]
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -1015,6 +1075,12 @@ version = "1.1.1+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "756daf9b1013ebe47a8776667b466417e2d4c5679d441c26230efd9ef78692db"
 
+[[package]]
+name = "typenum"
+version = "1.20.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40ce102ab67701b8526c123c1bab5cbe42d7040ccfd0f64af1a385808d2f43de"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
@@ -1066,6 +1132,12 @@ version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
 
+[[package]]
+name = "version_check"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
+
 [[package]]
 name = "vswhom"
 version = "0.1.0"