Summary

Return a proper error when a conversation is not found during chat initialization instead of panicking, and clean up stale/experimental code that accumulated around OAuth, Bedrock, and dependency management.

Context

The previous code used unwrap_or_default().expect(...) when looking up a conversation, which would panic with a confusing message if the conversation was missing. This PR replaces that with proper anyhow error propagation so callers receive a clean, descriptive error.

Alongside the bug fix, this PR removes several features and files that are no longer needed: the localhost OAuth callback server (and its tiny_http dependency), the Bedrock SanitizeToolIds transformer, the google_ai_studio provider, and the hex crate (replaced by format!("{:x}", ...) directly). The Bedrock provider model list is also restored to the stable set of GA models.

Changes

• Bug fix: find_conversation now propagates errors properly using ? and ok_or_else, returning "conversation {id} not found" instead of panicking
• Removed LocalhostOAuthCallbackServer: Deleted oauth_callback.rs (~526 lines) and removed the tiny_http dependency — the OAuth flow now always prompts the user to paste the authorization code
• Removed SanitizeToolIds Bedrock transformer: Deleted bedrock_sanitize_ids.rs (~269 lines) and its regex dependency from forge_repo
• Removed google_ai_studio provider: Cleaned up the ProviderId constant, display name mapping, from_str parsing, and related tests
• Removed id_token from OAuthTokenResponse: Field and associated enrichment logic for Codex OAuth removed; extract_chatgpt_account_id is now inlined directly where needed (device flow only)
• Replaced hex crate: SHA-256 hex encoding now uses format!("{:x}", hasher.finalize()) in both forge_app and forge_fs
• Dependency downgrades: sha2 pinned back to 0.10, similar to 2.4, rustyline to 17.0.2, posthog-rs to 0.4.7, toml_edit to 0.22 — aligning with upstream stable versions
• Bedrock provider list: Restored to the stable set of GA models (Titan, Anthropic Claude, Cohere, Meta Llama families), removing pre-release/experimental entries

Key Implementation Details

The conversation lookup change is minimal but impactful: unwrap_or_default().expect(...) was replaced with ? chaining through ok_or_else(|| anyhow::anyhow!("conversation {} not found", id)). This ensures any missing conversation surfaces as a structured anyhow::Error rather than a panic, which is then handled correctly by the caller.

The enrich_codex_oauth_credential helper was removed because the id_token field (its primary input) was removed from OAuthTokenResponse. The Codex device flow still extracts chatgpt_account_id from the access token directly.

Testing

# Run crate-level tests
cargo insta test --accept

# Verify the conversation not-found error surfaces correctly
cargo check -p forge_app

Links

• Related PR: fix(app): return error when conversation is not found #2852