Remove redundant ensureStableIds from Button Base

Context: src/button/Base.mjs contains a manual implementation of ensureStableIds which assigns a stable ID to the internal textNode. This manual assignment this.textNode.id = this.id + '__text' is redundant because stable IDs for child nodes should ideally be handled declaratively or by the core VDOM mechanism, or might not be strictly necessary if the node doesn't need to be referenced by ID for patching (if position-based diffing is sufficient).

However, ensureStableIds in src/button/Base.mjs was originally added as a "Workaround fix for: https://github.com/neomjs/neo/issues/6659". If we remove it, we need to ensure we don't regress on that issue.

Analysis: The text node is a child of the button. If the text node ID is critical for some external reason or specific diffing edge case, we should verify it. But generally, child nodes without keys/ids are diffed by index. The recent core changes to ensureStableIds in VdomLifecycle handle the root and wrapper IDs. They do not automatically assign IDs to every child node deep in the tree.

Goal: Remove ensureStableIds from src/button/Base.mjs if it's proven unnecessary, OR justify its existence. The user prompt suggests: "can we now remove ensureStableIds) ? => there is no point to assigning a spefic id to a child node."

If the text config setter (afterSetText) works by manipulating the VDOM node directly (which it does: textNode.text = value), then having a stable ID on that node isn't strictly required unless we are doing fine-grained updates via Neo.applyDeltas targeting that specific node ID, or if we need to find it via getVdomChild.

afterSetText in src/button/Base.mjs:

    afterSetText(value, oldValue) {
        let me         = this,
            isEmpty    = !value || value === '',
            vdomRoot   = me.getVdomRoot(),
            {textNode} = me;
        // ...
        me.update()
    }

It calls me.update(), which diffs the entire component VDOM. It does not use textNode.id to push a partial update.

Therefore, the explicit ID on the text node seems removable.

Verification: Run test/playwright/unit/button/Base.spec.mjs. One test Prototype VDOM mutation check specifically checks: expect(button1.textNode.id).toBe('my-button-1__text'); This expectation will fail if we remove the method. We should update the test to expect undefined (or no ID) if we remove the feature.

We need to confirm if removing it breaks anything else. Issue 6659 context is key but assuming user is correct that it's "no point".

I will create a task to remove it and update the tests.