feat(gradle): add Gradle ecosystem support with toml-span parser

Add deps-gradle crate supporting three Gradle manifest formats:
- Version Catalog (libs.versions.toml) via toml-span for reliable spans
- Kotlin DSL (build.gradle.kts) via regex parsing
- Groovy DSL (build.gradle) via regex parsing

Reuses MavenCentralRegistry from deps-maven for version resolution.
Extract shared LineOffsetTable, position_in_range, and
complete_package_names_generic to deps-core for DRY compliance.

Author: bug-ops

Cargo.toml

@@ -43,6 +43,7 @@ thiserror = "2"
 tokio = "1.49"
 tokio-test = "0.4"
 toml_edit = "0.25"
+toml-span = "0.7"
 tower-lsp-server = "0.23"
 tracing = "0.1"
 tracing-subscriber = "0.3"

crates/deps-core/src/lsp_helpers.rs

@@ -44,21 +44,6 @@ impl LineOffsetTable {
         Self { line_starts }
     }
 
-    /// Returns the byte offset of the start of the given 0-based line.
-    pub fn line_start_offset(&self, line: u32) -> usize {
-        self.line_starts.get(line as usize).copied().unwrap_or(0)
-    }
-
-    /// Returns the byte offset of the end of the given 0-based line (before newline).
-    pub fn line_end_offset(&self, content: &str, line: u32) -> usize {
-        let next_line = line as usize + 1;
-        if next_line < self.line_starts.len() {
-            self.line_starts[next_line].saturating_sub(1)
-        } else {
-            content.len()
-        }
-    }
-
     /// Converts a byte offset into an LSP `Position`.
     pub fn byte_offset_to_position(&self, content: &str, offset: usize) -> Position {
         let offset = offset.min(content.len());

crates/deps-gradle/Cargo.toml

@@ -19,7 +19,7 @@ async-trait = { workspace = true }
 regex = { workspace = true }
 thiserror = { workspace = true }
 tokio = { workspace = true }
-toml_edit = { workspace = true }
+toml-span = { workspace = true }
 tower-lsp-server = { workspace = true }
 tracing = { workspace = true }