fix(history): restore images during session replay

[epodivilov]

Summary

• replay embedded Codex history images as ACP image blocks with their original MIME type and bytes
• replay readable local history images through the same structured ACP image path, with an explicit link fallback when the file is unavailable or unsupported
• preserve non-image file mentions as ACP resource links while stripping Codex's synthetic attachment wrapper
• suppress attachment copies from JSONL fallback history so authoritative thread history emits each restored message and image once

Why

Codex stores replayable attachment structure in authoritative thread history, but the adapter currently converts it to Markdown links during session/load. This makes images that render correctly live turn into text links after a cold load.

Validation

• npm run typecheck
• npm test — 610 passed, 26 skipped
• npm run build
• targeted replay tests cover embedded images, readable local images, and authoritative/fallback deduplication

Related: #297
Task: ACP-295

Not verified

• npm run test:e2e requires CODEX_API_KEY or OPENAI_API_KEY, neither of which is available in this environment
• installing this build into acp-ws-codex.service, restarting the deployed bridge, and visually confirming a cold-loaded image in the client
• upstream GitHub workflows require maintainer approval before they can run on this fork PR