Support the installation and use of act to test and run GitHub workflows (#222)

* Support the use of `act` to test and run GitHub workflows

* Clarify text formatting instruction per review feedback

Updated the text formatting standard to explicitly state that the final
line must be non-empty and terminated with a single linefeed, leaving no
trailing blank lines. This clarification addresses potential ambiguity
in the previous wording.

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: greenc-FNAL <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

.actrc

@@ -0,0 +1,18 @@
+# act configuration for local workflow testing on the host
+# See: https://nektosact.com/usage/index.html
+#
+# NOTE: act cannot run inside the devcontainer due to nested container limitations.
+# Use this configuration when running act on the host machine.
+
+# Default image for jobs without explicit container
+# Medium = Ubuntu with common build tools
+-P=ubuntu-latest=catthehacker/ubuntu:act-latest
+
+# Container architecture
+--container-architecture=linux/amd64
+
+# Store artifacts in local directory
+--artifact-server-path=.act-artifacts
+
+# Optional: Use existing GitHub token if available
+# --secret-file=.secrets

.github/copilot-instructions.md

@@ -76,7 +76,7 @@ If the workspace root contains a `srcs/` directory, it may contain symbolic link
 
 **CRITICAL: Apply to ALL files you create or edit (bash scripts, Python, C++, YAML, Markdown, etc.)**
 
-- All text files must end with exactly one newline character and no trailing blank lines
+- All text files must have their final line be non-empty and terminated with a single newline character, leaving no trailing blank lines
 - **Never add trailing whitespace on any line** (spaces or tabs at end of lines)
 - This includes blank lines - they should contain only the newline character, no spaces or tabs
 - Exception: Markdown two-space line breaks (avoid; use proper paragraph breaks instead)

.gitignore

@@ -43,3 +43,6 @@ __pycache__/
 
 # macOS
 .DS_Store
+# act (local workflow testing)
+.act-artifacts/
+.secrets