fix: honor --top-k in interactive talk mode

[dex0shubham]

Problem

he talk <ka> -i -n 10 (interactive mode) ignores --top-k/-n. The talk command parses top_k and even prints it (Top K: {top_k}), but the interactive branch calls chat_loop(ka, ka_path) without it, and inside the loop ka.chat(query) runs with no top_k, falling back to the method default (top_k=3). The non-interactive branch correctly passes ka.chat(query, top_k=top_k).

Fix

Thread top_k through chat_loop:

• def chat_loop(ka, ka_path, top_k=3)
• ka.chat(query, top_k=top_k) inside the loop
• chat_loop(ka, ka_path, top_k=top_k) at the call site

Tests

tests/cli/test_talk.py: a stub KA records the top_k forwarded by chat_loop; asserts 10 is used, not the default. Fails on the pre-fix code.

ruff check/ruff format --check on hyperextract clean.