Surface T-shirt size elements in the backoffice admin

[Elena Peña Tapia (ElePT)]

Summary

The T-shirt size models (ComputeProfile, FunctionSize, Program.default_size) shipped in 0.36.0, but a function's size catalog (its sizes map) and its default size weren't surfaced in the backoffice admin where operators work. This PR adds them, and — as a second step — makes a Fleets function created purely in the admin actually runnable.

Part 1 — Surface the size elements

On the Program (Function) page

• FunctionSizeInline — a function's whole sizes map (each size key → compute profile) is now editable inline on its own page, mirroring the catalog the upload endpoint's sizes payload builds.
• default_size field in a new "Sizes" fieldset. Its dropdown is restricted to the function's own sizes (Program.clean() rejects a default belonging to another function).
• sizes_summary changelist column — N (default: s) or -.

On the ComputeProfile page

• sizes_using column — reference count, so an operator sees a profile is in use before editing/deleting it (the FK is PROTECT).

Both changelist columns are annotated to avoid per-row queries.

Part 2 — Make a backoffice-created Fleets function runnable

A Program created purely in the admin previously got only model defaults, skipping two runnable-critical steps the upload use case performs. Replicated here, reusing upload.py logic (single source of truth):

• CE project assignment. ProgramAdminForm.clean() assigns a Code Engine project to a Fleets function (provider's active project, or the deployment default) via CodeEngineProject.objects.assign_to_program, and blocks the save — with the upload endpoint's own message — when none is available. A Fleets function with no active CE project cannot run, so this fails loud rather than persisting a dead function.
• Default-size seeding. ProgramAdmin.save_related() seeds the deployment default size (DEFAULT_FUNCTION_SIZE → DEFAULT_FUNCTION_SIZE_PROFILE) for a size-less Fleets function. Runs after the inline FunctionSize formset, so an operator's declared sizes are respected; skipped when a default is already set. Non-fatal + warns when the profile is unregistered.

Refactor: extracted a module-level seed_default_size() (the use-case method now delegates) and promoted _no_ce_project_message → no_ce_project_message.

Scope

• Admin-only. No model or migration changes.
• Does not touch Job.compute_profile (the deprecated string) — that's a separate branch's concern.

Behavioral note (blocking tradeoff)

Because clean() blocks any Fleets save that can't get an active CE project, a legacy/misconfigured Fleets function whose provider has no active project (and no default configured) cannot be saved — even to disable it — until a project is assignable. This is the intended "fail-loud" behavior (mirrors the upload endpoint); the operator assigns a project in the same edit.

Testing

• gateway/tests/test_tshirt_admin.py (21 tests): inline rendering, default_size dropdown scoping, sizes_using count; CE auto-assign (provider + default paths), blocking when unconfigured / no project / inactive project, operator-chosen project preserved, Ray no-ops; default-size seeding (present/absent profile, no-clobber, sizes-declared), plus two end-to-end admin client tests proving the real add form blocks a non-runnable function and creates a runnable one.
• All admin + upload + size regression suites pass; manage.py check clean; pylint 10.00/10 on both source files; black clean.
• (Pre-existing, unrelated: test_http_server / test_function_access_client fail in this env without Redis/a running server — untouched by this PR.)