Parser: Treat javascript_tag content as foreign content

[marcoroth]

This pull request fixes how the parser handles javascript_tag do blocks when the body contains HTML-like syntax such as < operators in JavaScript expressions (e.g. n <o.length, for (let i = 0; i<items.length; i++)).

Previously, the outer HTML parser would interpret < inside a javascript_tag do body as an HTML tag opening, creating a broken HTMLOpenTagNode that swallowed the <% end %> closing tag. This caused a null dereference in the analyzer when it tried to access block_node->end_node.

The fix has two parts:

1. html parser option and foreign content re-parsing

   A new html parser option (defaults to true) controls whether the parser runs in HTML mode or foreign content mode. When html: false, the parser treats everything as literal text and ERB tags, no HTML tag parsing. The analyzer now re-parses javascript_tag do body content with html: false to produce clean LiteralNodes, regardless of what the outer HTML parse produced.

   New start_line and start_column options allow the re-parsed body to carry correct source locations from the original template.

2. Swallowed <% end %> recovery

   When the outer HTML parse swallows <% end %> inside a broken HTMLOpenTagNode, the analyzer walks the AST to find the swallowed ERBContentNode with end content. It creates a proper ERBEndNode from it and uses it as the close_tag, with stale ERBControlFlowScopeError cleared.

For example, the following template with action_view_helpers: true:

<%= javascript_tag do %>
  n <o.length
<% end %>

Now correctly produces:

@ DocumentNode (location: (1:0)-(3:9))
└── children: (1 item)
    └── @ HTMLElementNode (location: (1:0)-(3:9))
        ├── open_tag:
        │   └── @ ERBOpenTagNode (location: (1:0)-(1:24))
        │       ├── tag_opening: "<%=" (location: (1:0)-(1:3))
        │       ├── content: " javascript_tag do " (location: (1:3)-(1:22))
        │       ├── tag_closing: "%>" (location: (1:22)-(1:24))
        │       ├── tag_name: "script" (location: (1:4)-(1:18))
        │       └── children: []
        │
        ├── tag_name: "script" (location: (1:4)-(1:18))
        ├── body: (1 item)
        │   └── @ LiteralNode (location: (1:24)-(3:0))
        │       └── content: "\n  n <o.length\n"
        │
        ├── close_tag:
        │   └── @ ERBEndNode (location: (3:0)-(3:9))
        │       ├── tag_opening: "<%" (location: (3:0)-(3:2))
        │       ├── content: " end " (location: (3:2)-(3:7))
        │       └── tag_closing: "%>" (location: (3:7)-(3:9))
        │
        ├── is_void: false
        └── element_source: "ActionView::Helpers::JavaScriptHelper#javascript_tag"

Resolves #1426

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@1434

npx https://pkg.pr.new/@herb-tools/language-server@1434

npx https://pkg.pr.new/@herb-tools/linter@1434

commit: 8885aef

[github-actions]

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