chore: remove Bifrost LLM dispatch

[calvinmclean]

Related: obot-platform/nanobot#352

[Copilot]

Pull request overview

This PR removes the legacy Bifrost-based LLM proxy dispatch path and associated types, moving the system toward explicit, named LLM proxy routes and dialect handling.

Changes:

• Removed Bifrost request/streaming support from message policy evaluation and simplified dialect dispatch logic.
• Removed the gateway’s generic /api/llm-proxy/{path...} dispatch handler and the LLMProxyActivity model/migration entries.
• Updated token-usage tracking and tests to drop the Bifrost dialect and align with named proxy routes (e.g., generic-responses).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pkg/messagepolicy/evaluate.go	Removes Bifrost request types and Bifrost call path; tightens dialect dispatch via a switch.
pkg/gateway/types/activity.go	Removes LLMProxyActivity type.
pkg/gateway/server/router.go	Removes the generic /api/llm-proxy/{path...} route handler registration.
pkg/gateway/server/llmproxy.go	Removes dispatchLLMProxy and its request-body helper.
pkg/gateway/server/llmproxy_usage.go	Drops Bifrost dialect handling in token usage tracker selection.
pkg/gateway/server/llmproxy_test.go	Updates/cleans up proxy path tests to remove dispatch/bifrost cases.
pkg/gateway/db/db.go	Removes LLMProxyActivity from AutoMigrate set.
pkg/controller/handlers/nanobotagent/nanobotagent.go	Updates provider base URL derivation to use named routes (but currently leaves a broken fallback).
pkg/controller/handlers/nanobotagent/nanobotagent_test.go	Updates tests for named-route behavior and fallbacks (but currently expects a now-removed dispatch base URL for unknown providers).

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.