ci: CBM_REPRO_ONLY suite filter + reliable (ASan) fast lane

- repro_main: RUN_SUITE honors CBM_REPRO_ONLY (comma list of suite-name
  substrings) for fast targeted validation of a single fix.
- fast-repro.yml: ASan single-platform (the no-sanitizer build crashed some
  suites); single-platform is the speedup vs the 5-platform board.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

.github/workflows/fast-repro.yml

@@ -9,10 +9,10 @@ name: Fast Repro
 on:
   workflow_dispatch:
     inputs:
-      asan:
-        description: 'Build with ASan/UBSan (slower; needed for crash/UAF reds)'
-        type: boolean
-        default: false
+      suites:
+        description: 'Comma list of suite-name substrings to run (empty = all)'
+        type: string
+        default: ''
   push:
     branches: ['qa/fast-**']
 
@@ -27,13 +27,11 @@ jobs:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
       - name: Install deps
         run: sudo apt-get update && sudo apt-get install -y zlib1g-dev
-      - name: test-repro (fast, no sanitizers by default)
-        run: |
-          # No-ASan build is much faster and is enough for the extraction /
-          # attribution / invariant reds (the bulk). Crash/UAF reds need ASan
-          # → dispatch with asan=true, or rely on the full board.
-          if [ "${{ inputs.asan }}" = "true" ]; then
-            scripts/repro.sh CC=gcc CXX=g++
-          else
-            scripts/repro.sh CC=gcc CXX=g++ SANITIZE=
-          fi
+      - name: test-repro (single platform, ASan; CBM_REPRO_ONLY filters suites)
+        env:
+          # Optionally narrow to specific suites for a fast targeted check, e.g.
+          # CBM_REPRO_ONLY="repro_invariant_enclosing_parity,repro_grammar_systems".
+          # Empty = run all. (No-sanitizer builds crash on some suites, so ASan
+          # stays on; the single-platform run is the speedup vs the 5-platform board.)
+          CBM_REPRO_ONLY: ${{ github.event.inputs.suites }}
+        run: scripts/repro.sh CC=gcc CXX=g++

tests/repro/repro_main.c

@@ -27,12 +27,22 @@ int tf_skip_count = 0;
 
 #include "test_framework.h"
 
-/* Per-suite summary: redefine RUN_SUITE so every suite prints a one-line
- * "[SUITE] <name> P passed, F failed" report. Makes the board/fast-lane output
- * greppable for which suites still have reds without scraping every test line. */
+/* Per-suite summary + filter. RUN_SUITE prints a one-line
+ * "[SUITE] <name> P passed, F failed" report (greppable for which suites still
+ * have reds). When CBM_REPRO_ONLY is set (comma/space list of suite-name
+ * substrings), only matching suites run — for fast targeted validation of a
+ * single fix without rebuilding intent. */
+static int cbm_suite_enabled(const char *name) {
+    const char *only = getenv("CBM_REPRO_ONLY");
+    if (!only || !*only)
+        return 1;
+    return strstr(only, name) != NULL;
+}
 #undef RUN_SUITE
 #define RUN_SUITE(name)                                                                  \
     do {                                                                                 \
+        if (!cbm_suite_enabled(#name))                                                   \
+            break;                                                                       \
         int _p0 = tf_pass_count, _f0 = tf_fail_count;                                    \
         printf("\n%s=== %s ===%s\n", tf_dim(), #name, tf_reset());                       \
         suite_##name();                                                                  \