fix: remove mutable default arguments in SemanticRouter (follow-up to #700)

[harshadkhetpal]

Summary

Follow-up to #700 (merged last month): extensions/router/semantic.py has the same shared-mutable-default pattern (ruff B006) in code that wasn't covered there:

• SemanticRouter.__init__(connection_kwargs: dict[str, Any] = {})
• get_route_references(reference_ids: list[str] = [], keys: list[str] = [])
• delete_route_references(reference_ids: list[str] = [], keys: list[str] = [])

All five become | None = None. Unlike #700, no normalization statements are needed — I audited every use: __init__ already forwards connection_kwargs or None, and both methods only touch reference_ids/keys behind truthiness guards (if reference_ids:, if not keys: with reassignment before any iteration). So None behaves identically to the old shared {}/[] at every site, and the diff is just the five signature lines.

Testing

python -m py_compile passes; ruff check --select B006 on the file goes from 5 errors to clean.

🤖 Generated with Claude Code

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Note

Low Risk
Low-risk API signature fix with no new logic; omitted arguments behave like empty dict/list at existing guard sites.

Overview
Follow-up to #700: fixes ruff B006 in SemanticRouter by changing five parameters from shared mutable defaults ({} / []) to | None = None.

__init__: connection_kwargs now defaults to None instead of {}; existing connection_kwargs or None when initializing the index keeps behavior the same.

get_route_references / delete_route_references: reference_ids and keys default to None instead of []. Call sites already branch on truthiness (if reference_ids:, if not keys:) and assign lists before iteration, so no extra normalization was added.

Signature-only change; intended to stop cross-call state leaking through shared default objects.

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[vishal-bala]

Hi there, thanks for the PR! Can you update your branch from main? We have a patch to resolve the current CI issue.

[harshadkhetpal]

Done @vishal-bala — rebased onto current main (includes your CI patch). Same five-signature-line change, still normalization-free per the usage audit in the description.