Colour the editor view with relocated semantic tokens

The results document only ever got TextMate colouring, because a language
server will not serve semantic tokens for a `colored-refs` URI: there is no
file and no compilation behind it. So identifiers looked the way a C# file
does before the server has analysed it.

Instead of tokenizing anything ourselves, fetch the tokens for each *source*
file and move them:

- vscode.provideDocumentSemanticTokensLegend / provideDocumentSemanticTokens
  give the legend and the delta-encoded tokens for a real file. Neither is
  listed by getCommands(), so a test calls them to prove they exist rather
  than looking them up.
- Decode to absolute positions, keep the tokens on displayed lines, and shift
  each column by CODE_INDENT minus the stripped leading whitespace — the same
  mapping that places the highlight ranges. Re-encode with the source legend,
  so the type and modifier numbers stay meaningful.
- The legend is only known after a server answers, but
  registerDocumentSemanticTokensProvider wants it up front, so registration
  is deferred to the first search and redone if a later legend differs.
- Runs after the results are on screen and only changes colours, never text,
  so nothing waits on it. coloredReferences.semanticTokens turns it off;
  results over 40 files skip it.

Verified against DotRush: every relocated token covers exactly the text it
covered in the source file, and `Profiler` comes back typed as `class`.

README: drops the claim that semantic tokens would fix the panel's colours.
They supply the classification, never the colours, and webviews are not given
theme token colours — so only the editor view can be theme-exact. Feeding the
panel real token types is now roadmap item 5.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

package.json

@@ -160,6 +160,11 @@
           ],
           "default": "bottom",
           "description": "Where the results panel opens."
+        },
+        "coloredReferences.semanticTokens": {
+          "type": "boolean",
+          "default": true,
+          "description": "Colour the editor view with semantic tokens fetched from the source files, so identifiers look the way they do in the real file. Turn off to use TextMate grammar colouring only."
         }
       }
     },