fix: respect beautify ignore tags during range formatting

[maruthang]

Summary

Fixes #215

Bug: <!-- beautify ignore:start --> / <!-- beautify ignore:end --> directives were silently ignored by the formatter, causing content within ignore blocks to be reformatted.

Root Cause: Two issues: (1) When range-formatting inside an ignore block, the selected range did not include the ignore boundary comments, so js-beautify never saw them. (2) The directive regex in the bundled js-beautify required exact single spaces, rejecting comments with extra whitespace.

Fix: Added expandRangeToIgnoreBlock in htmlFormatter.ts to detect when a formatting range falls inside an ignore block and expand it to include the boundary comments. Relaxed the directive regex in both beautify-html.js and beautify-css.js to allow flexible whitespace.

Changes

• src/services/htmlFormatter.ts: Added expandRangeToIgnoreBlock() function that detects when a range falls within an ignore block and expands it to include the <!-- beautify ignore:start/end --> boundaries so js-beautify can recognise and skip the content.
• src/beautify/beautify-html.js: Relaxed __directives_block_pattern regex from requiring exact single spaces to allowing flexible whitespace (\s* / \s+).
• src/beautify/beautify-css.js: Same regex fix as beautify-html.js.
• src/test/formatter.test.ts: Added 4 regression tests covering full-document ignore blocks, range formatting inside ignore blocks, extra whitespace in ignore comments, and Go template syntax preservation.

Testing

• Added 4 regression tests in src/test/formatter.test.ts that verify ignore blocks are respected during both full-document and range formatting
• All 157 existing tests pass