fix: use regex match for CIRRUS_TAG to prevent L3 on branch pushes

$CIRRUS_TAG != '' evaluates true even when undefined. Switch to
=~ 'v.*' so L3 tasks only trigger on version tags.

Author: fullstackjam

.cirrus.yml

@@ -15,7 +15,7 @@ env:
 # =============================================================================
 release_validation_task:
   name: "E2E Release Validation"
-  only_if: $CIRRUS_TAG != '' || $CIRRUS_BRANCH == 'main'
+  only_if: $CIRRUS_TAG =~ 'v.*' || $CIRRUS_BRANCH == 'main'
   macos_instance:
     image: ghcr.io/cirruslabs/macos-sequoia-base:latest
   install_deps_script:
@@ -37,7 +37,7 @@ release_validation_task:
 
 full_journey_task:
   name: "E2E Journey Tests"
-  only_if: $CIRRUS_TAG != ''
+  only_if: $CIRRUS_TAG =~ 'v.*'
   macos_instance:
     image: ghcr.io/cirruslabs/macos-sequoia-base:latest
   install_deps_script:
@@ -53,7 +53,7 @@ full_journey_task:
 
 full_edge_cases_task:
   name: "E2E Edge Case Tests"
-  only_if: $CIRRUS_TAG != ''
+  only_if: $CIRRUS_TAG =~ 'v.*'
   macos_instance:
     image: ghcr.io/cirruslabs/macos-sequoia-base:latest
   install_deps_script:
@@ -69,7 +69,7 @@ full_edge_cases_task:
 
 full_commands_task:
   name: "E2E Command + Interactive Tests"
-  only_if: $CIRRUS_TAG != ''
+  only_if: $CIRRUS_TAG =~ 'v.*'
   macos_instance:
     image: ghcr.io/cirruslabs/macos-sequoia-base:latest
   install_deps_script: