ci: grant pull-requests:read so lint-pr-title workflow starts (#385)

**Requirements**

- [x] I have added test coverage for new or changed functionality — N/A
(CI workflow change only)
- [x] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [x] I have validated my changes against all supported platform
versions — N/A (CI workflow change only)

**Related issues**

- Root cause:
[launchdarkly/gh-actions#86](launchdarkly/gh-actions#86)
added `permissions: pull-requests: read` at the job level inside the
reusable lint-pr-title workflow
- Same fix as
[launchdarkly/sdk-meta#429](launchdarkly/sdk-meta#429)

**Describe the solution you've provided**

Adds `permissions: pull-requests: read` at the workflow level in
`.github/workflows/lint-pr-title.yml`.

A reusable workflow can only request a subset of the permissions the
caller has granted. Since this caller had no `permissions` block, the
reusable workflow's `pull-requests: read` request could not be
satisfied, causing every run to hit `startup_failure`.

**Describe alternatives you've considered**

Reverting the permission change in the reusable workflow, but that would
remove a security improvement (least-privilege scoping) across all
consumers.

**Additional context**

No product code is changed. The `Lint PR title` check on this PR itself
should exit `success` rather than `startup_failure`, confirming the fix.

Link to Devin session:
https://app.devin.ai/sessions/c7b96da5c9074500aa684bc9a9ba1c31
Requested by: @kinyoklion

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk CI-only change that adjusts GitHub Actions permissions; it
could only affect whether the PR title lint workflow is able to
start/run.
> 
> **Overview**
> Fixes the `Lint PR title` GitHub Actions workflow failing to start by
explicitly granting `pull-requests: read` at the workflow level,
ensuring the called reusable workflow can request PR read access.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
9f914f0. 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: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: kinyoklion

.github/workflows/lint-pr-title.yml

@@ -7,6 +7,9 @@ on:
       - edited
       - synchronize
 
+permissions:
+  pull-requests: read
+
 jobs:
   lint-pr-title:
     uses: launchdarkly/gh-actions/.github/workflows/lint-pr-title.yml@main