[HTExplicit]

Problem

Image Studio has had no model source since the Cindy removal, so it cannot create a job. The account tools still run through the indirection built for the plugin host, which is gone. A scan against upstream v0.2.13 also found fork-only symbols and fields that nothing reads. The owner's rule is that a retired feature leaves nothing behind.

Change

Image Studio is deleted

• Backend: service, runtime, repository, handler, the eight /api/v1/image-studio routes, GET/PUT /admin/settings/image-tools, wire providers. GATEWAY_IMAGE_STUDIO_ENABLED is no longer read.
• Frontend: the feature folder, the user page and its route, the navigation entry, i18n keys, the admin settings panel, image_studio_enabled in public settings.
• Live paths it touched (handler/openai_images.go, ops_error_logger.go, service/policy_context.go) are back in their upstream form.
• Migration 270_drop_image_studio.sql drops the three Image Studio tables and the image_tools_config setting. It does not touch plugin installations: the follow-up PR removes the retired first-party plugin rows as a whole.

Account tools are flattened

• The operation invoker, invocation and result types, native policy fixtures and the testextensions package are removed; folder, tag, bulk and import decisions are direct calls.
• The service-level filter branch of bulk taxonomy is removed. The handler resolves filter targets and checks expected_match_count itself, so the service only ever received account IDs.
• A request cancelled or timed out during validation no longer returns 503 ACCOUNT_TOOLS_UNAVAILABLE. Every other code, message and decision is unchanged.

Fork-only dead code

• Symbols and fields with no reader are removed, each judged by the commit that introduced it.
• Migration 271_drop_usage_billing_dedup_account_id.sql drops a column nothing reads. An older image fails billing writes without it, so a rollback needs ALTER TABLE usage_billing_dedup ADD COLUMN account_id BIGINT first; .downstream/native-domains.md has the procedure, including dropping the column again after returning to this version.
• QuotaActivityStamp.Revision stays: the quota estimate compares the whole struct.
• go.mod: github.com/pmezard/go-difflib is indirect again, as upstream has it.

Connection test

• Reasoning-effort validation errors are plain sentences again (reasoning effort is not supported by the selected account model) instead of a formatted application-error string.

Not in this PR

• production-deploy.yml, downstream-release.yml and deploy/ are identical to main. Their dead inputs and the GATEWAY_IMAGE_STUDIO_ENABLED lines are a separate task with the host deployer.

What an admin sees

• System settings → Gateway → Codex settings: the "Image tools" panel is gone.
• The Plugins page is unchanged here. The follow-up PR removes its retired first-party block as a whole.
• /image-studio is a 404 instead of a redirect to the dashboard.
• Previewed with mock data and approved by the owner before this PR.

Verification

• go build ./... (default and GOOS=linux); go vet ./... with no tag, -tags unit, and -tags integration on repository; wire diff clean; gofmt; go mod tidy -diff clean for go.mod.
• Migrations 270 and 271 applied on a throwaway PostgreSQL 18 from an empty database, with TestMigration270DropsImageStudio and TestMigration271DropsUsageBillingDedupAccountID.
• Targeted tests for quota measurement and activity, account taxonomy (unit and integration), bulk taxonomy handler, connection-test reasoning, account import decisions.
• vue-tsc, check:i18n, and the changed CI selector scripts.
• Two review passes with independent lenses (deletion completeness, live paths kept, account-tools behaviour, migration 271, frontend and CI). 16 findings confirmed in the second pass, all fixed; one of them restored Revision after an unchanged test showed it is read.

Not run locally: golangci-lint (the local binary cannot read Go 1.27 export data), the full unit and integration suites, frontend eslint and full vitest, real model calls. CI runs the required ones.

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