fix(inplace,embed): input set back mid-flight, report inputs, ambiguous anchors

Four items owed after S5b, reported by design-dev during the anti-slop run:

- carry() measured a sent-then-changed form against its OLD DEFAULTS. An
  answer set back mid-flight to the value the page first showed read as
  untouched, and the swap put the just-saved value over it. A form sent and
  then changed is now measured against its sent snapshot (sentSet.snapOf).
- The embed's clean-batch reload saw only our own forms. A report's own
  inputs lost whatever the operator had typed into them. Unsaved text in
  any control we don't own now holds the reload, and the page says so.
- Two r2b.toml rows ("D3 a stored theme...", "D3 forced light...") matched
  twice, so they proved only by where the first match fell. Both are
  re-anchored, and scripts/mutation_check.py now refuses any anchor that
  matches more than once. A new tool control covers that.
- The r2_flow contract's C3 steps 2 and 4 now say what S5b superseded. U3
  gains the report-input rule.

Mutation rows: u3_submit_all +1, r2_submit_all +1. Four rows were
re-anchored onto the moved lines.

tests/mutations/r2b.toml

@@ -384,8 +384,10 @@ label = "D3 a stored theme is not applied at load (a reload forgets it)"
 file = "booth/templates/base.html"
 test = "tests/test_flow_browser.py::test_the_theme_toggle_forces_light_and_dark_and_system_follows_the_os_live"
 old = '''
+      var t = localStorage.getItem('booth.theme');
       if (t === 'light' || t === 'dark') d.setAttribute('data-theme', t);'''
 new = '''
+      var t = localStorage.getItem('booth.theme');
       if (false) d.setAttribute('data-theme', t);'''
 
 [[mutation]]
@@ -402,8 +404,10 @@ label = "D3 forced light is not in the sheet"
 file = "booth/templates/_svos_tokens.css"
 test = "tests/test_flow_browser.py::test_the_theme_toggle_forces_light_and_dark_and_system_follows_the_os_live"
 old = '''
+/* ... or the viewer forced light. Same declarations as above, by construction. */
 :root[data-theme="light"] {'''
 new = '''
+/* ... or the viewer forced light. Same declarations as above, by construction. */
 :root[data-theme="light-OFF"] {'''
 
 [[mutation]]