ci: share the server repository's PR templates

Adopt the canonical PR template set from triton-inference-server/server
(default chooser plus internal/external contribution templates) so every
repository presents the same PR experience. The manual "Commit Type"
checkbox section is dropped — the conventional-pre-commit hook
(commit-msg stage) enforces it automatically.

TRI-1100

Author: mc-nv

.github/PULL_REQUEST_TEMPLATE/pull_request_template_external_contrib.md

@@ -0,0 +1,36 @@
+#### What does the PR do?
+<!-- Describe your pull request here. Please read the text below the line, and make sure you follow the checklist.-->
+
+#### Checklist
+- [ ] I have read the [Contribution guidelines](#../../CONTRIBUTING.md) and signed the [Contributor License
+Agreement](https://github.com/NVIDIA/triton-inference-server/blob/master/Triton-CCLA-v1.pdf)
+- [ ] PR title reflects the change and is of format `<commit_type>: <Title>`
+- [ ] Changes are described in the pull request.
+- [ ] Related issues are referenced.
+- [ ] Populated [github labels](https://docs.github.com/en/issues/using-labels-and-milestones-to-track-work/managing-labels) field
+- [ ] Added [test plan](#test-plan) and verified test passes.
+- [ ] Verified that the PR passes existing CI.
+- [ ] I ran pre-commit locally (`pre-commit install, pre-commit run --all`)
+- [ ] Verified copyright is correct on all changed files.
+- [ ] Added _succinct_ git squash message before merging [ref](https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html).
+- [ ] All template sections are filled out.
+- [ ] Optional: Additional screenshots for behavior/output changes with before/after.
+
+#### Related PRs:
+<!-- Related PRs from other Repositories -->
+
+#### Where should the reviewer start?
+<!-- call out specific files that should be looked at closely -->
+
+#### Test plan:
+<!-- list steps to verify feature works -->
+<!-- were e2e tests added?-->
+
+#### Caveats:
+<!-- any limitations or possible things missing from this PR -->
+
+#### Background
+<!-- e.g. what led to this change being made. this is optional extra information to help the reviewer -->
+
+#### Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)
+- closes GitHub issue: #xxx

.github/PULL_REQUEST_TEMPLATE/pull_request_template_internal_contrib.md

@@ -0,0 +1,36 @@
+#### What does the PR do?
+<!-- Describe your pull request here. Please read the text below the line, and make sure you follow the checklist.-->
+
+#### Checklist
+- [ ] PR title reflects the change and is of format `<commit_type>: <Title>`
+- [ ] Changes are described in the pull request.
+- [ ] Related issues are referenced.
+- [ ] Populated [github labels](https://docs.github.com/en/issues/using-labels-and-milestones-to-track-work/managing-labels) field
+- [ ] Added [test plan](#test-plan) and verified test passes.
+- [ ] Verified that the PR passes existing CI.
+- [ ] Verified copyright is correct on all changed files.
+- [ ] Added _succinct_ git squash message before merging [ref](https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html).
+- [ ] All template sections are filled out.
+- [ ] Optional: Additional screenshots for behavior/output changes with before/after.
+
+#### Related PRs:
+<!-- Related PRs from other Repositories -->
+
+#### Where should the reviewer start?
+<!-- call out specific files that should be looked at closely -->
+
+#### Test plan:
+<!-- list steps to verify -->
+<!-- were e2e tests added?-->
+
+- CI Pipeline ID:
+<!-- Only Pipeline ID and no direct link here -->
+
+#### Caveats:
+<!-- any limitations or possible things missing from this PR -->
+
+#### Background
+<!-- e.g. what led to this change being made. this is optional extra information to help the reviewer -->
+
+#### Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)
+- closes GitHub issue: #xxx

.github/pull_request_template.md

@@ -1,18 +1,13 @@
-#### What does the PR do?
-<!-- Describe the change and the motivation behind it. -->
+Thanks for submitting a PR to Triton!
+Please go the the `Preview` tab above this description box and select the appropriate sub-template:
 
-#### Related Issues / PRs
-<!-- Use "Closes #xxx" / "Fixes #xxx" / "Resolves #xxx" for issues.
-     Link related PRs from other triton-inference-server repositories. -->
+* [PR description template for Triton Engineers](?expand=1&template=pull_request_template_internal_contrib.md)
+* [PR description template for External Contributors](?expand=1&template=pull_request_template_external_contrib.md)
 
-#### Test plan
-<!-- How was this change verified? List steps, tests added, or CI evidence. -->
+If you already created the PR, please replace this message with one of
+* [External contribution template](https://raw.githubusercontent.com/triton-inference-server/server/main/.github/PULL_REQUEST_TEMPLATE/pull_request_template_external_contrib.md)
+* [Internal contribution template](https://raw.githubusercontent.com/triton-inference-server/server/main/.github/PULL_REQUEST_TEMPLATE/pull_request_template_internal_contrib.md)
+
+and fill it out.
 
-#### Caveats
-<!-- Optional: known limitations or follow-ups. -->
 
-#### Checklist
-- [ ] PR title follows `<commit_type>: <Title>` (conventional commit — enforced by the `conventional-pre-commit` hook)
-- [ ] I ran `pre-commit install && pre-commit run --all-files` locally and it passes
-- [ ] Copyright header is correct on all changed files
-- [ ] External contributors: I have read the [Contribution guidelines](../CONTRIBUTING.md) and signed the [Contributor License Agreement](https://github.com/NVIDIA/triton-inference-server/blob/master/Triton-CCLA-v1.pdf)