[CI] Add path-based triggers for niche workflows

Make expensive/niche workflows conditional on labels to reduce CI costs:

- docs.yml: Only builds docs on PRs when Documentation or tutorials/ label
  is present. Always builds on push to main/nightly/release.

- benchmarks_pr.yml: Only runs benchmarks when Performance or
  benchmarks/upload label is present. This is expensive (GPU, runs twice).

- test-linux-sota.yml: Only runs SOTA tests when sota-implementations/
  label is present. Always runs on push to main/nightly/release.

Labels are auto-applied by the file-based labeler (auto-labeler.yml) when
relevant files change, so developers don't need to manually add them.

Core library tests (test-linux.yml) continue to run on all PRs since
components are interconnected (e.g., replay buffers affect collectors).


ghstack-source-id: cfcd503
Pull-Request: #3403

Author: vmoens

.github/workflows/benchmarks_pr.yml

@@ -1,6 +1,12 @@
+# Continuous benchmarking for PRs
+#
+# Only runs when Performance or benchmarks/upload label is present.
+# This is expensive (GPU, runs twice for CPU/GPU comparison).
+# Add the label manually or use [Performance] prefix in PR title.
 name: Continuous Benchmark (PR)
 on:
   pull_request:
+    types: [opened, synchronize, labeled]
 
 permissions: write-all
 
@@ -13,6 +19,11 @@ concurrency:
 jobs:
 
   benchmark:
+    # Only run benchmarks when Performance or benchmarks/upload label is present
+    if: |
+      contains(github.event.pull_request.labels.*.name, 'Performance') ||
+      contains(github.event.pull_request.labels.*.name, 'performance') ||
+      contains(github.event.pull_request.labels.*.name, 'benchmarks/upload')
     name: ${{ matrix.device }} Pytest benchmark
     runs-on: linux.g5.4xlarge.nvidia.gpu
     strategy:

.github/workflows/docs.yml

@@ -1,4 +1,8 @@
 # This workflow builds the torchrl docs and deploys them to gh-pages.
+#
+# For PRs, docs are only built when the Documentation or tutorials/ label is present.
+# This is auto-applied by the file-based labeler when doc files change.
+# Always builds on push to main/nightly/release branches and tags.
 name: Generate documentation
 on:
   push:
@@ -10,6 +14,7 @@ on:
       - v[0-9]+.[0-9]+.[0-9]
       - v[0-9]+.[0-9]+.[0-9]+-rc[0-9]+
   pull_request:
+    types: [opened, synchronize, labeled]
   workflow_dispatch:
 
 concurrency:
@@ -24,6 +29,13 @@ permissions:
 
 jobs:
   build-docs:
+    # For PRs, only build docs when Documentation or tutorials/ label is present
+    # Always build on push (main/nightly/release/tags) and workflow_dispatch
+    if: |
+      github.event_name == 'push' ||
+      github.event_name == 'workflow_dispatch' ||
+      contains(github.event.pull_request.labels.*.name, 'Documentation') ||
+      contains(github.event.pull_request.labels.*.name, 'tutorials/')
     strategy:
       matrix:
         python_version: [ "3.12" ]

.github/workflows/test-linux-sota.yml

@@ -1,7 +1,13 @@
+# SOTA (State-of-the-Art) implementation tests
+#
+# For PRs, only runs when sota-implementations/ label is present.
+# This is auto-applied by the file-based labeler when sota files change.
+# Always runs on push to main/nightly/release branches.
 name: SOTA Tests on Linux
 
 on:
   pull_request:
+    types: [opened, synchronize, labeled]
   push:
     branches:
       - nightly
@@ -24,6 +30,12 @@ permissions:
 
 jobs:
   tests:
+    # For PRs, only run when sota-implementations/ label is present
+    # Always run on push (main/nightly/release) and workflow_dispatch
+    if: |
+      github.event_name == 'push' ||
+      github.event_name == 'workflow_dispatch' ||
+      contains(github.event.pull_request.labels.*.name, 'sota-implementations/')
     strategy:
       matrix:
         python_version: ["3.10"]