Use this first to discover the valid ``format`` strings before calling
``detect_format`` or ``parse_statement``. For the file extensions and a
human-readable description of each format, read the
``bankstatementparser://formats`` resource instead.

Returns:
    The supported format identifiers.

Use this when you hold statement text but do not yet know its format,
to resolve the ``format`` identifier from the content plus filename
hint. Once the format is known, call ``parse_statement`` to read the
transactions instead of calling this again.

Args:
    content: The raw statement text.
    filename: Original filename; its extension is the primary hint.

Returns:
    The detected format identifier.

Raises:
    ValueError: If the format cannot be detected.

Use this to read the full transaction detail plus the statement
balances from a payload. When you only need the balances/totals use
``summarize_statement`` instead, and to merely confirm a payload parses
without returning any rows use ``validate_statement``.

Args:
    content: The raw statement text.
    filename: Original filename; its extension selects the format
        when ``format`` is omitted.
    format: Explicit format override.
    limit: Optional cap on returned transaction rows.

Returns:
    A dict with the resolved ``format``, ``columns``, full
    ``transaction_count``, the (possibly truncated) ``transactions``
    as row dicts, and the statement ``summary``.

Raises:
    ValueError: If the format is unsupported or cannot be detected.

Use this to confirm a payload is well-formed and parseable before
committing to a full read; it returns a structured pass/fail with the
transaction count but never the rows themselves, and never raises on a
parse error. To actually read the transactions use ``parse_statement``.

Args:
    content: The raw statement text.
    filename: Original filename; its extension selects the format.
    format: Explicit format override.

Returns:
    A dict with ``is_valid``, the resolved ``format``, the
    ``transaction_count`` on success, and an ``error`` on failure.

Use this when you need just the opening/closing balances, currency, and
other summary fields without the per-transaction rows. For the full
transaction detail alongside the summary, use ``parse_statement``
instead.

Args:
    content: The raw statement text.
    filename: Original filename; its extension selects the format.
    format: Explicit format override.

Returns:
    The summary record with Decimal values stringified.

Raises:
    ValueError: If the format is unsupported or cannot be detected.