refactor(executor): split providers and preserve legacy entrypoints

Merge PR #1626 into codex/pr-1626

chore(executor): remove unused Openai-Beta header from Codex executor

feat: passthrough upstream response headers to clients

chore(runtime, registry): update Codex client version and GPT-5.3 model creation date

refactor(executor): centralize Codex client version and user agent constants

refactor(translator, executor): remove redundant `bytes.Clone` calls for improved performance

refactor(executor): optimize payload cloning and streamline SDK translator usage

refactor(codex): remove codex instructions injection support

fix(codex): avoid empty prompt_cache_key

fix(openai): drop stream for responses/compact

feat(openai): add responses/compact support

feat(executor): add request_id to error logs

feat(executor): apply payload rules using requested model

feat(registry): support provider-specific model info lookup

refactor(thinking): pass source and target formats to ApplyThinking for cross-format validation

feat(codex): enhance input transformation and remove unused `safety_identifier` field

fix(codex): ensure instructions field exists

fix(executor): properly handle thinking application errors

refactor: improve thinking logic

Fixed: #897

fix(codex): only override instructions in responses for OpenCode UA

feat(codex): add OpenCode instructions based on user agent

feat(executor): add HttpRequest support across executors for better http request handling

fix(server): resolve memory leaks causing OOM in k8s deployment

feat(executor): enhance payload translation with original request context

refactor(executor): resolve upstream model at conductor level before execution

fix(executor): use upstream model for thinking config and payload translation

feat(cliproxy): implement model aliasing and hashing for Codex configurations, enhance request routing logic, and normalize Codex model entries

refactor(thinking): export thinking helpers

fix(executor): add `allowCompat` support for reasoning effort normalization

Merge pull request #481 from sususu98/fix/increase-buffer-size

fix(runtime): unify reasoning effort metadata overrides

fix(runtime): validate reasoning effort levels

feat(runtime): add thinking config normalization

feat(util): implement dynamic thinking suffix normalization and refactor budget resolution logic

fix(executor): increase buffer size for stream scanners to 50MB across multiple executors

**feat(registry): add GPT-5.1 Codex Max model definitions and support**

**fix(runtime): simplify scanner buffer allocation in executor implementations**

**refactor(runtime): centralize reasoning effort logic for GPT models**

fix(runtime): remove gpt-5.1 minimal effort variant

**feat(runtime): extend executor support for GPT-5.1 Codex and variants**

**feat(runtime): add payload configuration support for executors**

Fixed: #246

feat(config): support HTTP headers across providers

fix(executor): remove default reasoning effort for `gpt-5-codex-mini`

fix(executor): update model name from `codex-mini-latest` to `gpt-5-codex-mini`

add default medium reasoning case for gpt-5-codex-mini

add default medium reasoning case for gpt-5-codex-mini

feat(registry): add GPT-5 Codex Mini model variants