Parser: Fix lambda block detection

[marcoroth]

This pull request updates the parser to correctly recognize lambda blocks (-> do / -> { and lambda do / lambda {) as ERB block openers.

Previously, code like <% content = -> do %> was parsed as an ERBContentNode and its corresponding <% end %> produced a false ERBControlFlowScopeError.

For an template like:

<% content = -> do %>
  Hello
<% end %>

It parsed as

@ DocumentNode (location: (1:0)-(4:0))
└── children: (4 items)
    ├── @ ERBContentNode (location: (1:0)-(1:21))
    │   ├── tag_opening: "<%" (location: (1:0)-(1:2))
    │   ├── content: " content = -> do " (location: (1:2)-(1:19))
    │   ├── tag_closing: "%>" (location: (1:19)-(1:21))
    │   ├── parsed: true
    │   └── valid: false
    │
    ├── @ HTMLTextNode (location: (1:21)-(3:0))
    │   └── content: "\n    Hello\n"
    │
    ├── @ ERBContentNode (location: (3:0)-(3:9))
    │   ├── errors: (1 error)
    │   │   └── @ ERBControlFlowScopeError (location: (3:0)-(3:9))
    │   │       ├── message: "`<% end %>` appears outside its control flow block. Keep ERB control flow statements together within the same HTML scope (tag, attribute, or content)."
    │   │       └── keyword: "`<% end %>`"
    │   │
    │   ├── tag_opening: "<%" (location: (3:0)-(3:2))
    │   ├── content: " end " (location: (3:2)-(3:7))
    │   ├── tag_closing: "%>" (location: (3:7)-(3:9))
    │   ├── parsed: true
    │   └── valid: false
    │
    └── @ HTMLTextNode (location: (3:9)-(4:0))
        └── content: "\n"

Now it correctly parses as:

@ DocumentNode (location: (1:0)-(4:0))
└── children: (2 items)
    ├── @ ERBBlockNode (location: (1:0)-(3:9))
    │   ├── tag_opening: "<%" (location: (1:0)-(1:2))
    │   ├── content: " content = -> do " (location: (1:2)-(1:19))
    │   ├── tag_closing: "%>" (location: (1:19)-(1:21))
    │   ├── body: (1 item)
    │   │   └── @ HTMLTextNode (location: (1:21)-(3:0))
    │   │       └── content: "\n    Hello\n"
    │   │
    │   └── end_node:
    │       └── @ 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))
    │
    └── @ HTMLTextNode (location: (3:9)-(4:0))
        └── content: "\n"

[github-actions]

🌿 Interactive Playground and Documentation Preview

A preview deployment has been built for this pull request. Try out the changes live in the interactive playground:

• Playground Preview
• Documentation Preview
• Website Preview

---

_{🌱 Grown from commit d3253ba}

---

✅ Preview deployment has been cleaned up.