Trace: add support for Codex #3657

Problem

Developers who use Codex need to capture their AI coding sessions with Chainloop Trace.

Expected behavior

Chainloop Trace supports Codex as a provider and produces AI coding session evidence from Codex sessions. Delivery has two milestones. Both are part of this task; the features in milestone 2 are required for Codex, even though their interfaces are optional in the shared provider architecture.

Milestone 1: Core Codex provider

Implementation: #3684 (open).

• Install, update, and uninstall native Codex hooks; support trace init --codex and trace run --codex.
• Capture session metadata, conversations, tool calls and results, models, token usage, and estimated cost.
• Render Codex conversations and tool exchanges in the existing session viewer.
• Attribute file edits and shell changes, including multi-file patches, and integrate with Git commit and push hooks.
• Support local evidence storage and control-plane uploads, with the welcome message and session link after push.
• Merge the implementation with its provider tests, live E2E checks, and compatibility documentation.

Milestone 2: Codex skills, spec pointers, and pasted images

These features are planned Codex work, not permanent exclusions from support.

• Implement trace.SkillTracker: record skills used during a Codex session and capture their contents in the session evidence.
• Implement trace.SpecCopyReplacer: replace duplicated spec-source reads and writes in the Codex transcript with pointers to the corresponding stored spec materials.
• Implement trace.PastedImageFinder: extract and deduplicate pasted images into image spec materials and replace inline transcript copies with pointers. Preserve inline data when extraction cannot succeed.
• Add compile-time interface checks for all three extensions.
• Add provider regressions and live Codex E2E coverage that verifies the captured skills, spec pointers, and pasted-image materials and pointers, including that they remain usable by the session viewer.
• Update the Codex compatibility table from the verified results and document any remaining limits.

Completion

Keep this task open after milestone 1 merges. Close it when both milestones are delivered and verified.

Who is affected

Developers who use Codex and Chainloop Trace.