feat(js_runtime): add multi-source Node version reading (#522)

Read Node.js version from multiple sources with priority:
1. .node-version file (highest)
2. engines.node in package.json
3. devEngines.runtime in package.json (lowest)

Key behaviors:
- Only write to .node-version when no version source exists
- Always fetch latest LTS from network when no version specified
- Warn when resolved version conflicts with lower-priority constraints
- node-semver handles partial versions natively (20, 20.18, etc.)

Author: fengmk2

Cargo.lock

@@ -79,6 +79,7 @@ heck = "0.5.0"
 hex = "0.4.3"
 httpmock = "0.7"
 ignore = "0.4"
+indicatif = "0.18"
 indexmap = "2.9.0"
 indoc = "2.0.5"
 infer = "0.19.0"

Cargo.toml

@@ -12,6 +12,7 @@ async-trait = { workspace = true }
 backon = { workspace = true }
 flate2 = { workspace = true }
 futures-util = { workspace = true }
+indicatif = { workspace = true }
 hex = { workspace = true }
 node-semver = { workspace = true }
 serde = { workspace = true }