[improvement] Configurable memory sidecar backend (auto/openai/claude/provider)

Memory sidecar backend is hardcoded to OpenAI/Claude, ignoring user's active provider

Problem

The memory sidecar auto-selects its LLM backend with this priority: OpenAI (if Codex credentials exist) > Claude > active provider. When Codex OAuth tokens are present but expired, the sidecar picks the OpenAI backend and every call fails with "OpenAI SSE error: unknown error". Memory extraction stops silently. No new memories are created. The user gets no warning.

This happens on any non-OpenAI provider (custom OpenAI-compatible gateways, Copilot, Gemini, Cursor, etc.) because the sidecar prefers stale Codex tokens over the user's actual working provider.

Root cause

In crates/jcode-base/src/sidecar.rs, auto_select_backend() checks auth::codex::load_credentials().is_ok() first. If Codex tokens exist (even expired), it picks OpenAI. The memory_model config only routes to OpenAI or Claude models. Any other model value falls back to auto_select_backend(), which still picks OpenAI.

There is no way to force the sidecar to use the active provider when Codex or Claude credentials exist.

Solution

Add a memory_sidecar_backend config option to [agents] in config.toml:

• "auto" (default): current behavior, auto-select OpenAI > Claude > provider
• "openai": force OpenAI Responses API
• "claude": force Claude Messages API
• "provider": dispatch through the active agent provider via complete_simple

This lets users on custom gateways (or any non-OpenAI/Claude provider) use their own model for memory extraction and relevance judging.

Config example

[agents]
memory_sidecar_backend = "provider"

Env override: JCODE_MEMORY_SIDECAR_BACKEND

Implementation

Available at: https://github.com/alecuba16/jcode/tree/feature/memory-sidecar-provider

Files changed (6 files, +132/-18):

• crates/jcode-config-types/src/lib.rs - new memory_sidecar_backend field in AgentsConfig
• crates/jcode-base/src/sidecar.rs - backend selection logic respects config override
• crates/jcode-base/src/config/env_overrides.rs - JCODE_MEMORY_SIDECAR_BACKEND env var
• crates/jcode-base/src/config/default_file.rs - documented in default config template
• crates/jcode-base/src/config/display_summary.rs - shows backend in config summary
• README.md - new ### Memory sidecar backend section with config table and examples

Start with crates/jcode-base/src/sidecar.rs and trace how AgentsConfig is loaded and how environment overrides are applied. Review the six files listed in the issue, then verify that the four backend values, the JCODE_MEMORY_SIDECAR_BACKEND override, the default config, summary output, and README documentation are consistent and support provider dispatch.