Report Builder: band keep-together toggle in the builder UI

[nielsdrost7]

Parent: #130 (Report Builder) · Related: #95 · Hanging item from #608

Story
As a company admin, I want to mark a band as "keep together" from the builder, so that band never splits across a page boundary in the PDF (e.g. the totals block).

Current state (as of PR #608)
The renderer already honors it: ReportRenderer::keepsTogether() wraps a band in page-break-inside: avoid when manifest.band_options.<band>.keep_together is true (covered by ReportRendererTest::it_marks_keep_together_bands_with_page_break_css). But nothing writes that flag — today it only works by hand-editing manifest.json. This is the remaining builder-side portion of the #95 page-break work (the manual PageBreak/Spacer bricks already shipped).

Acceptance criteria

• Each band in the builder page has a "keep together on one page" toggle (per-band, stored in manifest.band_options)
• Saving the builder persists the flag through ReportTemplateStorage::save() and it survives clone/rename
• Toggled bands render with page-break-inside: avoid; untoggled bands are unchanged
• PHPUnit: builder page test toggling the flag and asserting the persisted manifest + rendered CSS

[nielsdrost7]

SMART Plan — Report Builder: band keep-together toggle in the builder UI

Context/Epic: Core (Reports) — hanging follow-up from PR #608, parent #130; related #95

Specific

Company admins should be able to mark a band as "keep together" (never split across a page break) from the builder UI, persisted to manifest.band_options.<band>.keep_together. Current state on develop: this issue claims the renderer side already honors the flag via ReportRenderer::keepsTogether(), citing a specific test, ReportRendererTest::it_marks_keep_together_bands_with_page_break_css. Neither ReportRenderer nor any ReportRendererTest exists anywhere in this codebase today (confirmed by grep across Modules and every Tests directory) — this is the clearest signal that this entire cluster of Report Builder issues describes work living on the unmerged feature/130-report-builder branch (PR #608), not on develop. Until that PR lands (or is rebuilt from scratch), there is no renderer to toggle behaviour on and no builder page to put the toggle on.

Measurable

• Each band in the builder has a "keep together on one page" toggle, stored in manifest.band_options.
  • Frontend/Livewire: as a company admin I want to mark a band as keep-together so it never splits across a page break.

    #[Test]
    public function it_toggles_keep_together_for_a_band(): void
    {
        /* Arrange */
        $template = ReportTemplateStorage::clone('invoice/default', $this->company->id, 'Keep Together Test');

        /* Act */
        Livewire::actingAs($this->user)
            ->test(DesignReportTemplate::class, ['tenant' => Str::lower($this->company->search_code), 'slug' => $template->slug])
            ->call('toggleKeepTogether', ReportBand::FOOTER->value, true);

        /* Assert */
        $manifest = app(ReportTemplateStorage::class)->loadManifest($template->slug, $this->company->id);
        $this->assertTrue($manifest['band_options']['footer']['keep_together']);
    }

• The flag survives clone/rename.
  • PHPUnit: it_preserves_the_keep_together_flag_when_cloning_a_template()
• Toggled bands render with page-break-inside: avoid; untoggled bands are unchanged.
  • PHPUnit: it_renders_page_break_inside_avoid_only_for_toggled_bands()

Achievable

1. Blocked on [Reports]: Report Builder — bands + bricks #130/Report Builder: file-based persistence (manifest + bands JSON), clone + sync-system #528 (manifest persistence) and Report Builder: five band canvases (header, group header, details, group footer, footer) #523 (builder page to put the toggle on).
2. If PR [IP-130]: Report Builder — bands + bricks (IP-130, Phases 1-4 + Browsershot driver) #608 is abandoned, the fastest honest path is porting ReportRenderer::keepsTogether() and its cited test alongside the rest of Phase 3, then adding this builder-side toggle on top — not inventing the renderer behaviour independently.
3. Review PR [IP-130]: Report Builder — bands + bricks (IP-130, Phases 1-4 + Browsershot driver) #608 first, since it's the sole source claiming this renderer logic already works.

Relevant

This is the remaining builder-side portion of the #95 page-break work — the renderer behaviour is claimed done, but nothing lets a company admin actually turn it on without hand-editing manifest.json.

Time-bound

Sprint 7.