Add support for # style comments in {% liquid %} blocks

[Copilot]

Fixes the issue where lines starting with # inside {% liquid %} blocks were not treated as comments, causing the parser to skip subsequent statements.

Problem

Previously, when using # comments inside {% liquid %} blocks, the parser would stop processing statements after encountering the comment line:

{% liquid
  assign name = 'John'
  # very important information
  assign name = 'Jenna'
  echo name
%}

Expected output: Jenna
Actual output: `` (empty)

The assign name = 'Jenna' and echo name statements were being skipped.

Solution

Modified the LiquidTag parser to recognize # as a valid tag identifier in addition to regular identifiers. This allows the parser to properly handle # comments within liquid blocks by leveraging the existing inline comment infrastructure.

The key change is in FluidParser.cs, where the liquid tag parser now uses:

OneOf(Terms.Char('#').Then(x => "#"), Identifier).Switch(...)

This allows # to be recognized and processed by the InlineCommentTag handler, which correctly consumes the rest of the line as a comment (since inside liquid blocks, newlines act as tag terminators).

Testing

Added comprehensive test coverage:

• Basic # comment functionality
• Multiple comments in a single liquid block
• Empty comments (# with no content)
• Comments at the beginning and end of liquid blocks

All existing tests (1206) continue to pass, confirming backward compatibility.

Examples

Now works as expected:

{% liquid
  # required args:
  assign product = 'MyProduct'

  # optional args:
  assign should_show_border = true
  assign should_show_cursor = true
  
  echo product
%}

Output: MyProduct ✅

Regular inline comments outside liquid blocks continue to work:

{% # this is an inline comment %}
Hello World

Output: Hello World ✅

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Allow # style comments in the liquid tag</issue_title>
<issue_description>Inside {% liquid %} blocks, lines starting with # are not treated as comments. Instead, the parser skips the following statements.

Example:

{% liquid
  assign name = 'John'
  # very important information
  assign name = 'Jenna'
  echo name
%}

Observed behavior:

assign name = 'Jenna' is skipped because the parser treats the # line incorrectly.

Expected behavior:

Lines starting with # inside {% liquid %} should be treated as comments. All other statements should execute normally.

Goal:
Extend the parser so that both {% # comment %} and inline # comments inside {% liquid %} blocks are fully supported, aligning with standard Liquid behavior.

The example from the initial description:

{% liquid
  # required args:
  assign product = product

  # optional args:
  assign should_show_border = should_show_border | default: true
  assign should_show_cursor = should_show_cursor | default: true
%}

Originally posted by @MihaxXx in #833 (comment)</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #834

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