feat(tabs): Add last-tab-closable functionality

[macandcheese]

Related Issue: #14346

Summary

This adds a property to allow the last closable Tab to be closed.

We need to open a future breaking change issue to make this the default behavior. At that time, we should deprecate this newly added last-tab-closable.

[Copilot]

Pull request overview

Adds a lastTabClosable option for calcite-tabs so apps can preserve the close affordance when only one visible closable tab remains.

Changes:

• Adds lastTabClosable to calcite-tabs and forwards it to calcite-tab-nav.
• Updates tab-nav close-button hiding/restoration logic.
• Adds an e2e test for preserving the last close button.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/components/src/components/tabs/tabs.tsx	Defines and propagates the new tabs property.
packages/components/src/components/tab-nav/tab-nav.tsx	Implements last-visible-tab close button behavior and selection handling updates.
packages/components/src/components/tabs/tabs.e2e.ts	Adds coverage for retaining the close button with lastTabClosable.

[jcfranco]

We need to open a future breaking change issue to make this the default behavior. At that time, we should deprecate this newly added last-tab-closable.

I don’t see why we can’t keep this option around for a while and gather feedback before making further adjustments.

WRT changing the default behavior, the request to change the tab closing behavior recently came up since the feature was introduced in v1.4.0, so I have a hunch this may not be the majority use case. Curious if others have seen stronger demand for making this the default and setting up for removal later.

cc @Esri/calcite-pes

[isaacbraun]

Curious if others have seen stronger demand for making this the default and setting up for removal later.

I have not seen the demand, but others may have (re-pinging for timeliness) cc @Esri/calcite-pes.

Even if we keep it around for a while, we can open the issue to make it the default behavior where the reasoning could be documented which would be helpful when asking teams.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

[jcfranco]

Awesome! 🚀 Other than a few comments, this LGTM!

[jcfranco]

Suggestion: depending on how much direct element access is needed, locators could help simplify:

const reopenedTitle = page.locator("#tab-title-4");
const reopenedTab = page.locator("#tab-4");

await expect.element(reopenedTitle).toBeInTheDocument();

const reopenedTitleEl = await reopenedTitle.element() as TabTitle["el"];
reopenedTitleEl.closed = false;
await component.updateComplete;

await expect.element(reopenedTab).toBeInTheDocument();

await expect.element(reopenedTitle).toHaveProperty("closed", false);
await expect.element(reopenedTitle).toHaveProperty("hidden", false);
await expect.element(reopenedTitle).toHaveProperty("tabIndex", 0);

await expect.element(reopenedTab).toHaveProperty("hidden", false);
await expect.element(reopenedTab).toHaveProperty("selected", true);