fix(sourcemap): preserve names when collapsing sourcemap on minify (#10839) - #10871

Description

Fixes #10839

When minification and sourcemaps are enabled, oxc's codegen/mangler generates a sourcemap containing mangled identifier mapping names in last_map.names (e.g. ["greet", "personName"]), with the corresponding tokens referencing these names via name_id.

However, collapse_sourcemaps was only taking first_map.get_names() and original_token.get_name_id(). Since first_map (the pre-minification chunk map) had not mangled identifiers, its names list was empty and original_token.get_name_id() was None. As a result, the collapsed sourcemap had an empty names array and lost all token name_id references, preventing DevTools/debuggers from recovering the original symbol names.

Solution

1. Propagate Names Across Sourcemap Chain (rolldown_sourcemap):
   • In collapse_sourcemaps, trace name starting from token.get_name_id() on last_map.
   • As tokens are traced back through the chain, if an upstream sourcemap in the chain also has a name at that location (closer to the original source), that upstream name takes precedence (aligned with Rollup's collapseSourcemaps algorithm).
   • Pre-seed the output names table with any existing names from first_map, and append new unique names encountered during token tracing using a hash map lookup.
   • Set the 5th field of the collapsed token (name_id) to the mapped index in the consolidated names array.
2. Populate OutputAsset.names (rolldown):
   • In emit_sourcemap, populate OutputAsset.names from map.get_names() rather than hardcoding vec![].
3. Tests:
   • Added unit test test_collapse_sourcemaps_preserves_names_from_minifier in rolldown_sourcemap.
   • Added integration test fixture crates/rolldown/tests/rolldown/sourcemap/minify_sourcemap_names with node assertions verifying that sourceMap.names in dist/main.js.map contains the renamed identifiers (greet, personName).