Declutter estimate header action buttons (consolidated from #42–#54)

[Clarion1631]

Consolidates 10 duplicate requests (#42, #44, #46, #48, #49, #50, #51, #52, #53, #54) filed via the Help Chat Widget on Apr 6–7.

Problem

The action buttons in the estimate header/toolbar are too crowded — on both the estimate detail page and the estimate editor. Visual clutter hurts scannability and usability, especially on smaller screens.

Requested improvements (merged from all reports)

1. Keep only primary CTAs visible (e.g. Save, Send to Client); move secondary actions (Delete, Duplicate, Download PDF / print / export) into a … overflow menu.
2. Icon-only buttons with tooltips for secondary/common actions on smaller screens, expanding to icon+label on larger screens.
3. Responsive button bar that collapses into a dropdown below a viewport-width breakpoint.
4. Better spacing and visual hierarchy between the remaining buttons.
5. No functionality lost — every current action stays reachable.

Affected pages (from the original reports)

• Estimate detail header: /projects/…/estimates/…
• Estimate editor header/toolbar

Visual acceptance criteria

• Estimate header shows at most the primary CTAs plus one … overflow button; secondary actions (Delete, Duplicate, Download PDF) appear when the … menu is opened.
• At a narrow viewport (~375px wide), the header buttons do not wrap or overlap; actions collapse into the overflow menu.
• Every action available before the change is still reachable (visible or inside the … menu).

[claude]

Fix opened as #401 (branch claude/issue-399): #401

The estimate detail page and the editor turned out to be the same component, and its … overflow menu already held every secondary action — so the real remaining defect was responsiveness. The PR stops the centred Builder / Costing & Expenses tabs from painting over the surrounding clusters below 1280px, collapses labels to icons (with tooltips + aria-labels) on small screens, moves the Client/Internal toggle into the … menu below 640px, and adds e2e/estimate-header-responsive.spec.ts covering 1440px and 375px. No action was removed.