test(validation): negative load-error checks; keep run logs out of the repo

load_errors_check.py loads deliberately broken .tum fixtures in batch on the
build under test (like lsp_check.py) and asserts each fails with its specific
located message and without a raw traceback. Wired into run.sh just before the
main suite, so it runs for every channel.

The run validation items now point their sub-instance log at the gitignored
report dir, so a GUI run no longer litters the tree with sub_*.log files.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/validation/load_errors/bad_include.tum

@@ -0,0 +1,9 @@
+main:
+  name: root
+  steps:
+    - sleep:
+        name: ok
+        timeout: 0
+    # The structural error lives in the included file; the message must point
+    # the user at that file, not at this one.
+    - !include bad_include_inc.tum

test/validation/load_errors/bad_include_inc.tum

@@ -0,0 +1,4 @@
+# Included as a bare list of steps. The unknown item below must be reported
+# with THIS file as the location.
+- frobnicate_in_include:
+    name: nope

test/validation/load_errors/group_no_steps.tum

@@ -0,0 +1,6 @@
+main:
+  name: root
+  steps:
+    # A container item (group) without its mandatory 'steps:' list.
+    - group:
+        name: g

test/validation/load_errors/scalar_body.tum

@@ -0,0 +1,5 @@
+main:
+  name: root
+  steps:
+    # The body of an item must be a mapping of parameters, not a scalar.
+    - sleep: 5

test/validation/load_errors/step_not_mapping.tum

@@ -0,0 +1,5 @@
+main:
+  name: root
+  steps:
+    # A step that is a bare scalar instead of a '<item>: ...' mapping.
+    - just some text

test/validation/load_errors/two_steps.tum

@@ -0,0 +1,11 @@
+main:
+  name: root
+  steps:
+    # Two items wrongly packed under a single '-' marker (a frequent indent
+    # mistake): the second key belongs one '-' lower.
+    - sleep:
+        name: s
+        timeout: 0
+      group:
+        name: g
+        steps: []

test/validation/load_errors/unknown_action.tum

@@ -0,0 +1,8 @@
+main:
+  name: root
+  steps:
+    - console:
+        console_name: c1
+        steps:
+          - opens:
+              device: /dev/ttyUSB0

test/validation/load_errors/unknown_item.tum

@@ -0,0 +1,5 @@
+main:
+  name: root
+  steps:
+    - frobnicate:
+        name: nope