…-pick PRs targeting release branch (#29658)

## **Description**

Re-introduces the release-branch skip in
`.github/actions/smart-e2e-selection/action.yml`.

The original logic was added in #28331 and accidentally removed by
#29305 ("ci: add automated E2E readiness label and CI checks - Part1"),
which refactored the action and didn't carry the release-branch handling
forward. Since the merge of #29305, every cherry-pick PR targeting
`release/*` runs the AI-based reduced E2E selection — same as a `main`
PR — instead of running the full suite.

Why release branches deserve different handling (same reasoning as
#28331):

- On `main`, iterating quickly with a risk-scored subset is a reasonable
trade-off — we accept some residual risk for speed and catch the rest in
follow-up PRs.
- A PR into `release/*` is effectively "this build is a candidate to
ship." Release cherry-picks are low-volume and high-impact, and we
cannot afford to merge a cherry-pick that breaks CI on the release
branch under release urgency.


## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes: https://consensyssoftware.atlassian.net/browse/INFRA-3464 

## **Manual testing steps**


## **Screenshots/Recordings**

### **Before**


### **After**

> ⏭️ **Smart E2E selection skipped** - PR targets a release branch
(release/\*)
>
> All E2E tests pre-selected.

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

Made with [Cursor](https://cursor.com)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk CI-only change that just alters when the composite action
runs AI selection vs defaulting to the full E2E suite; main risk is
unintentionally skipping AI selection if `base-ref` is mis-set.
> 
> **Overview**
> **Smart E2E selection now skips AI for PRs targeting `release/*`.**
The `smart-e2e-selection` composite action adds a `check-release-target`
gate using `inputs.base-ref`; when it matches `release/*`, the action
bypasses checkout/deps/analysis and keeps the default
`ai_e2e_test_tags=["ALL"]` with `ai_confidence=100`.
> 
> The action’s `base-ref` input description is updated to document this
behavior, and the AI analysis step now reports a specific skip reason
for release-branch targets (in addition to the existing skip-label
behavior).
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
94855dc. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Co-authored-by: Cursor <cursoragent@cursor.com>