Add archive helpers and harden task runtime

site/doc/pages/yaml_decode.txt

@@ -0,0 +1,57 @@
+:sig
+DTree yaml_decode(String s)
+
+:params
+s : YAML source string
+return value : decoded DTree
+
+:see
+>markup
+yaml_encode
+json_decode
+xml_decode
+0_DTree
+
+:content
+Parses a practical YAML subset into a `DTree`.
+
+`yaml_decode()` is designed for concise UCE config files. It intentionally avoids full YAML schema behavior and does not support anchors, aliases, tags, directives, or complex inline collection syntax.
+
+Try the live example in the [YAML demo](../demo/yaml.uce).
+
+Example:
+
+```uce
+String source = "app:\n"
+	"  name: UCE Starter\n"
+	"  debug: true\n"
+	"  port: 8080\n"
+	"  paths:\n"
+	"    - site\n"
+	"    - cache\n";
+
+DTree cfg = yaml_decode(source);
+
+cfg["app"]["name"].to_string();       // UCE Starter
+cfg["app"]["debug"].to_bool();        // true
+cfg["app"]["port"].to_s64();          // 8080
+cfg["app"]["paths"]["1"].to_string(); // cache
+```
+
+Supported syntax:
+
+- indentation-based maps
+- indentation-based lists
+- `key: value` map entries
+- list entries with `- value`
+- quoted strings with single or double quotes
+- booleans `true` and `false`
+- empty/null-ish values as empty strings
+- comments beginning with `#` outside quoted strings
+- literal block strings with `|`
+- folded block strings with `>`
+- optional `---` and `...` document markers
+
+Numeric-looking values are stored as strings, matching `json_decode()`'s current behavior. Use `to_s64()`, `to_u64()`, or `to_f64()` when reading numeric config values.
+
+Malformed input raises a request-visible `yaml_decode(): ...` runtime error.