runtests.tcl: fix multiple trailing file tails collapsing into one glob

Two independent list-flattening bugs made `runtests.tcl foo.test bar.test`
match zero files, forcing agents to run files individually:

- the trailing glob value is -multiple 1, so its parsed value is a list;
  plain lappend nested it as a single space-containing element
- punk::path::treefilenames declares tailglobs as a -multiple 1 positional
  (one glob per argument), but the whole file_globs list was passed as one
  argument, re-collapsing it (this also broke multiple globs supplied via
  -tcltestoptions {-file {...}})

Single names always worked because a one-element Tcl list flattens to
itself, which masked both bugs. Verified: two file tails now discover and
run both suites (files=2, 40/40 pass).

Also note multi-file-tail support in src/tests/AGENTS.md Work Guidance.

Assisted-by: harness=claude; primary-model=claude-fable-5; api-location=anthropic.com

src/tests/AGENTS.md

@@ -37,6 +37,7 @@ Top-level test harness and source-tree tests for ShellSpy/Punk. Tests here exerc
 - Use `-include-paths` with paths relative to `src/tests/`, using forward slashes. The flag accepts a space-separated list of glob patterns and may also be repeated, with all occurrences accumulating (`-multiple 1` as of 2026-07-10; previously the last flag silently won).
 - Use `-tcltestoptions {-match <test_name>}` for focused single-test runs.
 - For agent-efficient focused runs, prefer `<tcl_interpreter> src/tests/runtests.tcl -report compact -show-passes 0 -include-paths <relative/path/**> <file-tail.test>`.
+- Multiple trailing file tails are supported and match independently: `runtests.tcl foo.test bar.test` runs both in one invocation (fixed 2026-07-17; previously multiple names collapsed into one glob matching zero files).
 - Treat `RUNTESTS_RESULT status=warn` and compact warning reasons such as `missing-cleanupTests` as incomplete test results, even if observed pass events are listed.
 - Add `-slowest <n>` when timing outliers are relevant.
 - Add `-strict-exit 1` when a nonzero shell exit code is needed for failures or parser warnings.

src/tests/runtests.tcl

@@ -439,7 +439,9 @@ if {[dict exists $tcltestoptions -file]} {
 }
 
 if {[dict exists $received glob]} {
-    lappend file_globs [dict get $values glob]
+    #glob is -multiple 1: $values glob is a list of the supplied names - expand,
+    #or multiple file tails collapse into one space-containing glob matching nothing
+    lappend file_globs {*}[dict get $values glob]
 }
 #fall back to default if still empty
 if {[llength $file_globs] == 0} {
@@ -498,7 +500,8 @@ dict set tallydict files_with_warnings   [list]
 set file_summaries [list]
 set all_passes [list]
 
-set testfiles [punk::path::treefilenames -dir $test_base -tailbase $test_base -exclude-files $exclude_files -include-paths $include_paths $file_globs]
+#tailglobs is a -multiple 1 positional: each glob must be a separate argument, or multiple globs collapse into one
+set testfiles [punk::path::treefilenames -dir $test_base -tailbase $test_base -exclude-files $exclude_files -include-paths $include_paths {*}$file_globs]
 
 if {[dict exists $tcltestoptions -singleproc] && [dict get $tcltestoptions -singleproc]} {
     if {!$report_json_only} {