ci(e2e): trigger E2E Test pipeline on new release/* branches

[KayMKM]

What

Add a CI trigger to the Modelkit E2E Test pipeline so each push to a release/* branch (including the initial push that creates a new release branch) automatically runs the pipeline.

trigger:
  batch: true
  branches:
    include:
      - release/*

Why

Today the E2E Test pipeline only runs:

• Manually (queue-time), or
• Daily at 00:00 UTC+8 on main.

When a new release/* branch is cut, there is no automatic E2E validation against it. This change ensures every new release branch gets an E2E run as soon as it's pushed, so we catch release-specific regressions before publishing.

Behavior

• New release branch created -> fires on the initial push (which is how a branch is created in git), giving us the "trigger when a new release branch appears" semantics.
• Subsequent commits on a release branch -> also trigger a run. Release branches typically see few commits, so this is acceptable.
• batch: true -> coalesces rapid successive pushes into a single run, avoiding contention on the shared self-hosted agents (QNN / OV / AMD).
• Daily main schedule -> unchanged.
• PRs -> still not triggered; E2E failures don't block PR merges.

[DingmaomaoBJTU]

LGTM — small focused change, logic is correct. Two minor points left in comments (scheduled runs on release branches and batch semantics) but neither blocks the core goal.