fix(cli): resolve relative paths before computing file URI

[cursor]

Bug & impact

The bigos parse CLI crashed with ValueError: relative path can't be expressed as a file URI whenever the user passed a relative path — e.g. the exact invocation shown in the README quickstart:

bigos parse contract.pdf --format=md

Reproduction (slightly trimmed):

$ bigos parse contract.pdf --format=md
Traceback (most recent call last):
  ...
  File "/workspace/src/bigos/cli.py", line 84, in parse
    source = Source(uri=path.as_uri(), mime_type=mime, sha256=sha256_file(path))
                        ^^^^^^^^^^^^^
  File ".../pathlib.py", line 467, in as_uri
    raise ValueError("relative path can't be expressed as a file URI")
ValueError: relative path can't be expressed as a file URI

Impact: every documented quickstart invocation from a normal working directory aborts before any parsing happens. The CLI is the primary entry point of the package, so this is high blast-radius user-facing breakage.

Root cause

Path.as_uri() is only defined for absolute paths. Typer/Click's default Path parameter (resolve_path=False) hands the user-supplied string through verbatim, so path in the parse command stayed relative. The as_uri() call therefore raised on any relative input.

Fix

src/bigos/cli.py: resolve the input path to absolute (path.resolve()) before calling as_uri(), and reuse the resolved path for sha256_file() so the URI and the hashed bytes always refer to the same canonical location.

-    mime = mimetypes.guess_type(path)[0] or "application/octet-stream"
-    source = Source(uri=path.as_uri(), mime_type=mime, sha256=sha256_file(path))
+    mime = mimetypes.guess_type(path)[0] or "application/octet-stream"
+    abs_path = path.resolve()
+    source = Source(uri=abs_path.as_uri(), mime_type=mime, sha256=sha256_file(abs_path))

Validation

• New regression test test_cli_relative_path_does_not_crash_with_value_error in tests/test_cli.py invokes the CLI through Typer's CliRunner with a relative path (using a stub backend) and asserts the resulting Source.uri is a valid absolute file:// URI.
• Full test suite: pytest -m "not slow" → 54 passed; pytest tests/test_cli.py (incl. slow Docling parse tests) → 6 passed.
• No other behavioural changes; the fix is a one-line .resolve() plus a passthrough.