feat(cli): improve file discovery and completion

- Render remote files as an aligned table with JSON and TSV alternatives.
- Add Bash and Zsh completion for commands, options, paths, and remote files.
- Allow downloads by exact filename while rejecting ambiguous duplicate names.
- Cover table formatting, completion scripts, and selector resolution with tests.

cli/nanoshare_client/table.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from collections.abc import Iterable
+
+def _display_width(value: str) -> int:
+  return len(value)
+
+def _cell(value: object) -> str:
+  return '' if value is None else str(value)
+
+def format_table(headers: list[str], rows: Iterable[Iterable[object]]) -> str:
+  string_rows = [[_cell(value) for value in row] for row in rows]
+  widths = [_display_width(header) for header in headers]
+  for row in string_rows:
+    for index, value in enumerate(row):
+      if index < len(widths):
+        widths[index] = max(widths[index], _display_width(value))
+
+  def render_row(values: list[str]) -> str:
+    padded = [value.ljust(widths[index]) for index, value in enumerate(values)]
+    return '  '.join(padded).rstrip()
+
+  separator = '  '.join('-' * width for width in widths).rstrip()
+  lines = [render_row(headers), separator]
+  lines.extend(render_row(row) for row in string_rows)
+  return '\n'.join(lines)