Support inline # comments on TypedDict and dataclass fields

[hemanth1999k]

Fixes #242.

Currently the only way to document a field is the verbose Annotated[int, Doc("...")] syntax. This adds support for native Python inline comments:

class Point(TypedDict):
    x: int  # X-coordinate
    y: int  # Y-coordinate

which produces the same TypeScript as before:

interface Point {
    // X-coordinate
    x: number;
    // Y-coordinate
    y: number;
}

Uses inspect.getsourcelines + ast to pull # comments off field definitions at schema-generation time. Annotated/Doc still takes priority when both are present. Fails silently for dynamically-defined types (REPL, exec, etc.) so nothing breaks.

Adds three snapshot tests covering TypedDict inline comments, Doc-takes-priority, and dataclass inline comments.

[hemanth1999k]

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[hemanth1999k]

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[robgruen]

I really like the idea of this PR. Having inline comments would be fantastic. However, I noted a few different schemas that could break the implementation as provided. Instead of doing a find string, use the Python tokenizer to get each raw AST token and then grab the contents of the comment token.

Here's a suggestion from copilot (requires importing io & tokenize):

def _extract_inline_field_comments(py_type: type) -> dict[str, str]:
    """Return a mapping of field name -> trailing '#' comment for a TypedDict/dataclass."""
    try:
        source_lines, _ = inspect.getsourcelines(py_type)
    except (OSError, TypeError):
        # Source unavailable (e.g. dynamically created types) -> no comments.
        return {}

    source = textwrap.dedent("".join(source_lines))

    # Only real COMMENT tokens count. A '#' inside "..." is a STRING token, so it's ignored.
    comment_by_line: dict[int, str] = {}
    try:
        for token in tokenize.generate_tokens(io.StringIO(source).readline):
            if token.type == tokenize.COMMENT:
                comment_by_line[token.start[0]] = token.string[1:].strip()
    except (tokenize.TokenError, IndentationError):
        pass  # keep whatever we gathered before an incomplete-source error

    if not comment_by_line:
        return {}

    try:
        tree = ast.parse(source)
    except SyntaxError:
        return {}

    comments: dict[str, str] = {}
    for node in ast.walk(tree):
        if isinstance(node, ast.ClassDef):
            for stmt in node.body:
                if (
                    isinstance(stmt, ast.AnnAssign)
                    and isinstance(stmt.target, ast.Name)
                    and stmt.end_lineno is not None
                ):
                    comment = comment_by_line.get(stmt.end_lineno)
                    if comment:
                        comments[stmt.target.id] = comment
    return comments

[robgruen]

This will cause problems....see these schemas that break:

# BREAK 1 — hex colors, NO comment intended
class Theme(TypedDict):
    background: Literal["#FFFFFF", "#000000"]
    accent: Literal["#FF0000"]

# BREAK 2 — real comment gets corrupted (string '#' comes first)
class Swatch(TypedDict):
    color: Literal["#00FF00"]  # the accent color as a hex triplet

# BREAK 3 — dataclass default
@dataclass
class GitConfig:
    comment_marker: str = "value # not a comment"

# BREAK 4 — URL fragment in a default leaks out
@dataclass
class ApiEndpoint:
    url: str = "https://api.example.com/v1/items#latest"

# BREAK 5 — multi-line annotation whose last line has '#' in a string
class ButtonSpec(TypedDict):
    variant: Literal[
        "primary",
        "hash-#-danger"]  # pick one variant