feat(repl): repository commands %repo, %projects, %load and %publish over the SysML v2 API

[devin-ai-integration]

What and why

The sysml REPL and the Jupyter kernel gain the four repository commands of the OMG pilot's Jupyter kernel, with its grammar:

%repo [<BASE PATH>]
%projects
%load [--id=<PROJECT ID>] [--name=<NAME>] [--branch=<BRANCH NAME or ID>] [<NAME>]
%publish [-d] [--project=<PROJECT NAME>] [--branch=<BRANCH NAME>] <NAME>

They work against any server speaking the standard SysML v2 API (/projects, /branches, /commits with change payloads, /elements, /roots) — the pilot's SysML-v2-API-Services, which wants no token — and against Flexo MMS, whose extras (bearer token, organization, Layer 1 Turtle, ETag pushes) stay optional.

• Transport. The standard API client is now internal/translate/interop/sysmlapi (projects, branches, commits, elements, roots, optional bearer token, typed StatusError/UnreachableError); internal/translate/interop/flexo wraps it and keeps Layer 1, orgs and ETag semantics. Paging follows a server's Link: rel="next" to the end even when a page is short, which the pilot server does. sysml -sync is unchanged and its tests pass as they were.
• Shared sync. internal/translate/interop/modelsync holds what sysml -sync and the REPL share: baseline/apply over reposync.Diff/reposync.Apply, provenance scope (ProjectRef), the rooted cut of a model, notation writing, and the derived-property filter. There is no second sync implementation.
• REPL. %repo shows or sets the session's base URL (seeded from FLEXO_SYSMLV2_URL, plain-HTTP guard honoured, token read only from FLEXO_INTEROP_TOKEN and never printed or persisted). %projects lists <name> (<id>) over every page. %load resolves the project by name/--id/--name and the branch by name or id (default branch when absent), reads the head's elements, writes them as notation and submits them as a document, recording project/branch/commit so a later %publish without --branch commits on that branch; a name two projects share is refused naming both ids. A lone argument that is a path on disk still loads files. %publish cuts the elements rooted in a session-resolved qualified name, creates the project when none has that name, otherwise commits the diff against the branch head, reporting the commit id and created/updated/deleted counts; -d sends every derived property the exporter computes, without it the ones the reader recomputes are left out. The REPL reaches the transport through a replext.Repository extension and does not import cmd/sysml.
• Errors. Syntax and argument problems are *repl.UsageError, which the kernel now answers as UsageError for every meta command; server failures carry the HTTP status and the server's message.
• Docs. "Working with a repository" in the Jupyter guide (environment for the pilot server and for Flexo), the kernel reference, the REPL command reference, %help, and a changelog fragment.

How it was verified

• go build ./..., go vet ./..., gofmt -l . (empty).
• go test ./internal/translate/interop/... ./internal/frontend/... ./cmd/sysml/... — pass. New tests: an httptest fake of the standard API (projects, branches, commits with change, elements, roots, Link paging, 404, 409) driving all four commands through Session.RunMeta, including a %publish → %load round trip into a fresh session that compares the models, a %load --branch=<non-default> followed by a %publish that must commit on that branch, usage errors, completion of flags and project names, %help; a Jupyter engine test over %repo/%projects/UsageError/CommandError; modelsync tests pinning the derived-property set against every example model.
• make test-short — pass apart from TestFormattingDiffIsCheaperThanFormatting (an LSP timing test unrelated to this change) under the full-suite load; it passes with -count=3 on its own.
• make man-check, make docs-check, python3 scripts/changelog.py check — pass. tests/hygiene layering passes with the new packages.
• Live Flexo MMS stack (Fuseki + Layer 1 + SysML v2 API from the flexo-mms-sysmlv2 compose files), driven through the built bin/sysml: %repo show/set, the plain-HTTP guard, %projects empty and populated, %publish creating a project (9 created) then committing an edit (2 created, 1 updated, no second project), --project/--branch to another project and branch, -d confirmed by API readback (owningClassifier present only after a derived publish, a repeat is a no-op), %load by name, --id, --name and --branch into fresh sessions with the notation preserved, publish after load committing on the loaded branch (default and non-default), clean errors for a missing project, missing branch, unresolved root and unreachable server, %help and Tab completion of flags and live project names; sysml -sync diff/apply then no-op against the same stack. No token appeared in any transcript.
• The opt-in TestFlexoInterop expectation gate was run against that stack and fails three comparisons (74 → 76 subjects, 240 → 268 identity triples, sysx:sourceLine/sourceColumn/sourceEndLine/sourceEndColumn now among the uncarried properties); it fails identically on origin/develop, so the drift predates this branch and the expectation is left for its own change.
• Not verified against the OMG pilot SysML-v2-API-Services server.

Checklist

• make test and make lint pass locally
• Tests added or updated for the change
• Documentation extended where it already covers the surface (see CONTRIBUTING.md)
• Changelog entry added as changes/unreleased/<slug>.<section>.md, not as an edit to CHANGELOG.md
• baselines regenerated and make docs-counts run if a gate count moved (compliance rows need nothing: the census is counted at docs build)
• No internal work-item labels (waves, slices, F4, K5) in the body, docs, or changelog

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/5c4ff33730224c458b08de0632279da1
Open in Devin Desktop: https://nasa-jpl-demo.devinenterprise.com/desktop/session/5c4ff33730224c458b08de0632279da1?variant=devin
Requested by: @HuiJun

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring

[devin-ai-integration]

Rebased onto feat/load-notebook (#1004) so the two can merge in sequence. Besides the textual merges in meta.go's command table and docs/reference/repl-commands.md, the rebase had to reconcile the two %load extensions, which both parse -- options:

• loadsRepository now routes a %load to the repository only on a repository option (--id, --name, --branch) or a lone name that names no path. Before, any -- option was taken as a project load, so with the repository linked (as the sysml binary has it) %load --cells 1,3 nb.ipynb would have been refused as "--cells is not an option of %load".
• namesPath counts an .ipynb extension as a path, like .sysml/.kerml, so a notebook that is missing is reported as an unreadable file rather than a project that doesn't exist.
• An unknown option of the file form is now a *UsageError (as the repository form's already was), whose lines carry usageLoadPath, the repository usage when one is linked, and the "unknown option" message; usageLoadPath is the notebook-aware usage line, and meta.go prints it from the constant.
• The prefixed helper added here duplicated the one complete.go gained from feat(repl): draw named elements on demand with the pilot kernel's %viz #1000; the copy here is dropped.

TestLoadWithCellsReadsANotebookNotAProject covers the first two points with the repository linked; TestLoadRefusesWhatItCannotRead reads every line of a usage error for its "unknown option" case.