feat: add syntax highlighting for 9 additional languages

- Cargo.toml: Add tree-sitter grammars for Nix, Python, JavaScript,
  TypeScript, Go, C, CSS, HTML, YAML. Upgrade tree-sitter-highlight
  to 0.26 for language version 15 compatibility.

- src/highlight.rs: Add Language enum variants and get_config()
  match arms for all new languages. Update render() callback for
  0.26 API (writes attributes to buffer). Add tests for Nix and
  Python highlighting.

TOML excluded due to incompatible API (tree-sitter 0.20 vs 0.26).

Cargo.lock

@@ -511,12 +511,21 @@ dependencies = [
  "maud",
  "pulldown-cmark",
  "serde",
- "thiserror 2.0.18",
+ "thiserror",
  "toml 0.8.23",
  "tree-sitter-bash",
+ "tree-sitter-c",
+ "tree-sitter-css",
+ "tree-sitter-go",
  "tree-sitter-highlight",
+ "tree-sitter-html",
+ "tree-sitter-javascript",
  "tree-sitter-json",
+ "tree-sitter-nix",
+ "tree-sitter-python",
  "tree-sitter-rust",
+ "tree-sitter-typescript",
+ "tree-sitter-yaml",
  "walkdir",
 ]
 
@@ -926,6 +935,7 @@ version = "1.0.149"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "83fc039473c5595ace860d8c4fafa220ff474b3fc6bfdb4293327f1a37e94d86"
 dependencies = [
+ "indexmap",
  "itoa",
  "memchr",
  "serde",
@@ -1009,33 +1019,13 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "55937e1799185b12863d447f42597ed69d9928686b8d88a1df17376a097d8369"
 
-[[package]]
-name = "thiserror"
-version = "1.0.69"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b6aaf5339b578ea85b50e080feb250a3e8ae8cfcdff9a461c9ec2904bc923f52"
-dependencies = [
- "thiserror-impl 1.0.69",
-]
-
 [[package]]
 name = "thiserror"
 version = "2.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4288b5bcbc7920c07a1149a35cf9590a2aa808e0bc1eafaade0b80947865fbc4"
 dependencies = [
- "thiserror-impl 2.0.18",
-]
-
-[[package]]
-name = "thiserror-impl"
-version = "1.0.69"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 2.0.114",
+ "thiserror-impl",
 ]
 
 [[package]]
@@ -1116,13 +1106,14 @@ checksum = "5d99f8c9a7727884afe522e9bd5edbfc91a3312b36a77b5fb8926e4c31a41801"
 
 [[package]]
 name = "tree-sitter"
-version = "0.24.7"
+version = "0.26.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a5387dffa7ffc7d2dae12b50c6f7aab8ff79d6210147c6613561fc3d474c6f75"
+checksum = "974d205cc395652cfa8b37daa053fe56eebd429acf8dc055503fee648dae981e"
 dependencies = [
  "cc",
  "regex",
  "regex-syntax",
+ "serde_json",
  "streaming-iterator",
  "tree-sitter-language",
 ]
@@ -1138,18 +1129,67 @@ dependencies = [
 ]
 
 [[package]]
-name = "tree-sitter-highlight"
-version = "0.24.7"
+name = "tree-sitter-c"
+version = "0.24.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6411813e4a9ebc87d391b98b0f3ce65d5361cd80c54de8651d8b85b555ea5d95"
+checksum = "1a3aad8f0129083a59fe8596157552d2bb7148c492d44c21558d68ca1c722707"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
+[[package]]
+name = "tree-sitter-css"
+version = "0.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5cbc5e18f29a2c6d6435891f42569525cf95435a3e01c2f1947abcde178686f"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
+[[package]]
+name = "tree-sitter-go"
+version = "0.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c8560a4d2f835cc0d4d2c2e03cbd0dde2f6114b43bc491164238d333e28b16ea"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
+[[package]]
+name = "tree-sitter-highlight"
+version = "0.26.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb0636662a03005d9289649e0b4a89ff37b75df5033e8d4a16398740ae6496d2"
 dependencies = [
- "lazy_static",
  "regex",
  "streaming-iterator",
- "thiserror 1.0.69",
+ "thiserror",
  "tree-sitter",
 ]
 
+[[package]]
+name = "tree-sitter-html"
+version = "0.23.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "261b708e5d92061ede329babaaa427b819329a9d427a1d710abb0f67bbef63ee"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
+[[package]]
+name = "tree-sitter-javascript"
+version = "0.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68204f2abc0627a90bdf06e605f5c470aa26fdcb2081ea553a04bdad756693f5"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "tree-sitter-json"
 version = "0.24.8"
@@ -1166,6 +1206,26 @@ version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4ae62f7eae5eb549c71b76658648b72cc6111f2d87d24a1e31fa907f4943e3ce"
 
+[[package]]
+name = "tree-sitter-nix"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4952a9733f3a98f6683a0ccd1035d84ab7a52f7e84eeed58548d86765ad92de3"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
+[[package]]
+name = "tree-sitter-python"
+version = "0.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6bf85fd39652e740bf60f46f4cda9492c3a9ad75880575bf14960f775cb74a1c"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "tree-sitter-rust"
 version = "0.23.3"
@@ -1176,6 +1236,26 @@ dependencies = [
  "tree-sitter-language",
 ]
 
+[[package]]
+name = "tree-sitter-typescript"
+version = "0.23.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c5f76ed8d947a75cc446d5fccd8b602ebf0cde64ccf2ffa434d873d7a575eff"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
+[[package]]
+name = "tree-sitter-yaml"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53c223db85f05e34794f065454843b0668ebc15d240ada63e2b5939f43ce7c97"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "unicase"
 version = "2.9.0"