refactor(bundle-size): convert API classes to factory functions

[layershifter]

Summary

Convert API classes behind get* entry points (and UncontrolledAPI) from class to factory functions returning a closed-over public surface. Class scaffolding (constructor + private field declarations + arrow-bound method properties) doesn't mangle as well as plain top-level functions and closures, so each getX consumer ships less code.

8 APIs converted, one commit per API:

• RestorerAPI
• OutlineAPI
• DeloserAPI
• GroupperAPI
• MoverAPI
• ModalizerAPI
• CrossOriginAPI
• UncontrolledAPI

Pattern

// before
export class RestorerAPI implements Types.RestorerAPI {
    private _tabster: TabsterCore;
    private _history: History;
    constructor(tabster: TabsterCore) { ... }
    dispose(): void { ... }
    private _onFocusIn = (...) => { ... };
    createRestorer(...) { ... }
}

// after
export function createRestorerAPI(tabster: TabsterCore): Types.RestorerAPI {
    const history = new History(tabster.getWindow);
    const onFocusIn = (...) => { ... };
    // ... wiring (event listeners, queueInit, subscriptions)
    return {
        createRestorer(...) { ... },
        dispose() { ... },
    };
}

Private fields → closure variables. Arrow-bound private methods → local const arrows. Constructor body → factory body. Public API → returned object. The interface in Types.ts is unchanged; consumers in src/get/*.ts swap new XAPI(...) for createXAPI(...).

Static methods

DeloserAPI had static methods (getDeloser, getHistory, forceRestoreFocus) used from CrossOrigin.ts. Kept under a same-named const DeloserAPI = { ... } namespace so call sites continue to work unchanged. Internal state needed by the statics is exposed via a _-prefixed internal interface.

Bundle-size impact

Measured against master (post-#529). All getX fixtures shed bytes; per-API factory savings were ~570 B – 2.3 kB minified depending on API size.

Fixture	Master	This PR	Δ min	Δ gzip
all exports	113.84 kB / 30.94 kB	105.63 kB / 30.17 kB	−8.21 kB	−773 B
createTabster (core)	39.76 kB / 11.89 kB	39.65 kB / 11.88 kB	−108 B	−13 B
getCrossOrigin	110.62 kB / 30.24 kB	103.00 kB / 29.56 kB	−7.62 kB	−683 B
getDeloser	49.27 kB / 14.23 kB	48.02 kB / 14.15 kB	−1.24 kB	−83 B
getGroupper	47.00 kB / 13.59 kB	45.91 kB / 13.54 kB	−1.09 kB	−54 B
getModalizer	49.07 kB / 14.38 kB	47.61 kB / 14.23 kB	−1.46 kB	−153 B
getMover	54.65 kB / 15.89 kB	53.57 kB / 15.82 kB	−1.09 kB	−67 B
getObservedElement	45.56 kB / 13.48 kB	45.46 kB / 13.47 kB	−108 B	−12 B
getOutline	48.87 kB / 14.22 kB	46.60 kB / 13.96 kB	−2.27 kB	−255 B
getRestorer	42.52 kB / 12.52 kB	41.84 kB / 12.46 kB	−677 B	−56 B

OutlineAPI was the biggest individual win — many small private helper methods compress better as closure-captured locals. getCrossOrigin shows the cumulative effect since it bundles every other API.

Out of scope

Three groups of remaining classes were intentionally not converted:

• Subscribable family — KeyboardNavigationState, FocusedElementState, ObservedElementAPI, plus the two CrossOrigin-internal subscribable classes all extend a shared Subscribable<A,B> base. Converting requires a coordinated migration of the base and all 5 subclasses in one PR. Estimated additional savings: ~500 B in core. Worth doing as a follow-up.
• RootAPI — has heavy external static usage (RootAPI.getTabsterContext, RootAPI.getRoot called from Modalizer/Focusable/etc.). Doable with the same const-namespace trick used for DeloserAPI, but the blast radius warrants its own PR.
• FocusableAPI — no external statics, mechanical conversion. Skipped only to keep this PR focused; trivial follow-up.

Verification

• npm run type-check (lib + tests + stories) passes
• npm run lint:check passes
• npm run format:check passes
• Full test suite — runs in CI

Behavior changes

None. The public interfaces in Types.ts are unchanged; only the runtime construction differs (new XAPI(...) → createXAPI(...)). All call sites are in src/get/*.ts and src/Tabster.ts.

🤖 Generated with Claude Code

[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
tabster all exports	113.84 kB 30.937 kB	90.654 kB 27.848 kB	-23.186 kB -3.089 kB
tabster createTabster (core)	39.761 kB 11.892 kB	18.093 kB 6.352 kB	-21.668 kB -5.54 kB
tabster findAllFocusable	0 B 0 B	21.206 kB 7.332 kB	🆕 New entry
tabster findLastFocusable	0 B 0 B	21.251 kB 7.349 kB	🆕 New entry
tabster findNextFocusable	0 B 0 B	21.237 kB 7.343 kB	🆕 New entry
tabster findPrevFocusable	0 B 0 B	21.251 kB 7.347 kB	🆕 New entry
tabster getCrossOrigin	110.623 kB 30.244 kB	88.178 kB 27.162 kB	-22.445 kB -3.082 kB
tabster getDeloser	49.268 kB 14.234 kB	30.668 kB 10.048 kB	-18.6 kB -4.186 kB
tabster getGroupper	47 kB 13.593 kB	34.122 kB 11.424 kB	-12.878 kB -2.169 kB
tabster getModalizer	49.072 kB 14.378 kB	35.553 kB 11.889 kB	-13.519 kB -2.489 kB
tabster getModalizer (with dummy inputs)	0 B 0 B	38.108 kB 12.59 kB	🆕 New entry
tabster getMover	54.653 kB 15.887 kB	41.065 kB 13.516 kB	-13.588 kB -2.371 kB
tabster getObservedElement	45.564 kB 13.484 kB	22.295 kB 7.795 kB	-23.269 kB -5.689 kB
tabster getOutline	48.867 kB 14.216 kB	24.519 kB 8.366 kB	-24.348 kB -5.85 kB
tabster getRestorer	42.518 kB 12.52 kB	20.498 kB 7.076 kB	-22.02 kB -5.444 kB

_{🤖 This report was generated against a579ebbd50e37f1565551549fe57bbc9ddafab64}