Upgrade Deno from 2.7.7 to 2.7.12

Updates mise.toml and .github/actions/setup-deno/action.yaml to use
Deno 2.7.12.  Also excludes SVG and HTML files from the Deno formatter
in deno.json, as Deno 2.7.12's formatter is not idempotent on these
files.

Assisted-by: Claude Code:claude-sonnet-4-6

Author: dahlia

.github/actions/setup-deno/action.yaml

@@ -6,4 +6,4 @@ runs:
   steps:
   - uses: denoland/setup-deno@v2
     with:
-      deno-version: 2.7.7  # Keep in sync with mise.toml
+      deno-version: 2.7.12  # Keep in sync with mise.toml

deno.json

@@ -98,7 +98,9 @@
   },
   "fmt": {
     "exclude": [
-      "**/*.md"
+      "**/*.html",
+      "**/*.md",
+      "**/*.svg"
     ]
   },
   "nodeModulesDir": "auto",

mise.toml

@@ -1,6 +1,6 @@
 [tools]
 bun = "1.2.22"
-deno = "2.7.7"
+deno = "2.7.12"
 node = "22"
 pnpm = "10.28.0"