fix: use Console().print for token usage and remove spurious space in…

[aryanputta]

Fixes #75

Two bugs in src/rosa/rosa.py are fixed in this PR.

Purpose

_print_usage was calling print() with rich markup strings. Plain print() does not interpret rich markup, so show_token_usage=True printed literal bracket tags instead of formatted text. Replaced with Console().print() and added the missing Console import from rich.console.

In astream, the token accumulation read final_output += f" {content}", prepending a space before every token. When no on_chain_end event provides a final output, the fallback string recorded to chat history started with a leading space. Changed to final_output += content.

Proposed Changes

• [FIX] _print_usage: replaced print() with Console().print() so rich markup renders correctly
• [ADD] from rich.console import Console
• [FIX] astream: removed spurious leading space in token accumulation

Issues

• Fixes fix: _print_usage renders rich markup as plain text and astream accumulates tokens with spurious leading spaces #75

Testing

• Verified _print_usage with show_token_usage=True renders bold labels correctly in terminal
• Verified astream chat history entries no longer start with a leading space
• No existing tests broken