feat(cli): group the help by task and wrap it

[devin-ai-integration]

What and why

sysml -help was 463 lines: 84 flags in one alphabetical list, each alias an entry of its own, arguments typed (string, value) rather than named, 21 descriptions over 200 characters unwrapped, and a mistyped flag dumped the whole list after the error. %help had 24 commands under no heading.

The usage.Doc model gains option groups, and the terminal help and the manual page render them from the same table:

type Doc struct { ...; Options []OptionGroup; ... }
type OptionGroup struct { Title string; Options []Option }
type Option struct { Name string; Aliases []string; Arg string }   // usage.Opt("eval", "<expr>", "e")
func (d Doc) CheckOptions(fs *flag.FlagSet) error                    // every flag in exactly one group
func (d Doc) WriteHint(w io.Writer)                                  // synopsis + "Run 'sysml -help' for the options."

• sysml -help: flags under 14 task headings (General, Evaluating, Checking a model, Running behaviors, Analysis engines, Checking every schedule, Converting and migrating, Compiling natively, Rendering views, Rendering documents, Styling HTML documents, Syncing against a repository, Diagnostics and profiling, Deprecated), spelled once with the shorthand folded in (-e, -eval <expr>, -o, -output <file>, -satisfy[=<name>]), description wrapped in the column beside it. Examples come before the options (Section.BeforeOptions).
• Descriptions shortened to a line or two; the detail they carried moves into the section on that mode (Checking a model, new Running actions and state machines and Checking every schedule, Analysis engines, Conversion, Rendering a view). The -pdf-* trio and -to sit under Deprecated as "Former name of -doc-…".
• Misuse: flag.Usage is doc().WriteHint, so a bad flag prints the error, the synopsis and one pointer line on stderr.
• Man page: each group is an .SS, each option a .BR \-e ", " \-eval " \fIexpr\fP" tag; man/man1/sysml.1 regenerated. sysml-lsp and sysml-grpc declare no groups and render as before.
• %help: the ungrouped commands come under Session, Settings, Analysis engines and Checking every schedule; descriptions wrap into a 28-column gutter, a signature wider than that takes a line of its own (folded at 72 for %check-bounds), %exit is noted beside %quit. Table entries are written {name: …, group: …} so examples/self_model_test.go's source check still finds them.

Line-width contract unchanged: no help line exceeds 96 columns (options wrap at 78); the help is now 609 lines, all of it grouped and readable. Not in this PR: a short-card -help with -help <topic> / %help <command>, which needs a one-line summary per flag and is a separate change.

How it was verified

• New: TestGroupedOptionsFoldAliasesAndWrap, TestCheckOptionsFindsStrayFlags (internal/frontend/usage), TestEveryFlagIsInOneOptionGroup (cmd/sysml — fails when a flag is registered without a group), TestHelpTextIsGroupedAndWrapped (internal/frontend/repl — headings, folded alias, signature fold, width).
• Updated: TestStreamsAndStatus expects -convert <format> in -h and the three-line answer to --nosuchflag; TestPrintUsageStatesTheExperimentalNotice renders against docFlags().
• go build ./..., go vet ./..., gofmt -l . (empty), go test ./..., make man-check, python3 scripts/changelog.py check, scripts/check-doc-ids.py all pass.
• By hand: sysml -h, sysml --nosuchflag, man -l man/man1/sysml.1, %help in the REPL.

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

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Runtime verification

Revision 91a090d51 exercised through the built CLI, the man pager and the interactive REPL.

CLI help	REPL help

Misuse	Rendered manual

• All 84 flag spellings appear exactly once across 14 groups; the examples precede the options; descriptions align at column 30 and no line exceeds 96 columns (609 lines).
• -h and -help give identical stdout, empty stderr, status 0. An unknown flag and a flag missing its argument each give exactly three stderr lines, no stdout, status 2.
• man -l renders the grouped subsections, -e, -eval expr and -satisfy[=name]; the emitted roff matches the committed page; make man-check and mandoc -T lint are clean.
• %help shows the nine headings, column-28 descriptions, width ≤ 78, the folded %check-bounds signature and %exit beside %quit; %hlep still suggests %help, tab completion works, %quit and %exit both exit 0.
• Regression spot-checks: -e/-eval and -v/-version agree; -o/-output write identical Turtle and the round-tripped SysML validates; -pdf-toc and -doc-toc produce identical HTML with a table of contents.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.