docs: the reseq probe's readings, and the invariants resequencing changes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/claude/invariants-plot-and-layout.md

@@ -104,6 +104,29 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   figure rebuild — which `assign()` already forces. A signal on no plot gets
   `RowSet::unplotted_color()` (grey) rather than no chip, so the panel's rows stay the
   same height.
+- **The invalid-span band is data-anchored and reserves no layout space.** `Plot::set_invalid_spans()`
+  draws a tinted quad over the span it names; unlike `Plot::set_x_note()` (the `t0` caption), which
+  is chrome drawn at a fixed corner of the axes regardless of the data, a band pans and zooms with
+  the samples it accuses. The two are the complementary cases: the caption is chrome that data does
+  not move, the band is annotation that data does. Both are alike in the second count: neither
+  reserves layout space and neither can be picked, so a hole cannot move the layout the labels were
+  measured into.
+
+  The band has a **one-device-pixel floor on its width**. A hole of one sample in a window of hundreds
+  of thousands is a hundredth of a column, and a fill rounded to zero would drop exactly the case
+  the band is most needed for — a sub-pixel hole is invisible as a gap in the polyline and would be
+  invisible as a band too without the floor.
+
+  The band carries **three states** and they are a property of the hole, not of the plot: solid
+  (`Style::invalid_fill`) while the hole still lacks packets, faint (`Style::invalid_repaired_fill`)
+  once `Hole::repaired()` is true, absent once the hole's slots age out of the ring and
+  `forget_holes_before()` drops it from the table. A repaired hole is **not** retired early: the band
+  is a record of what the window was missing, and retiring it on repair would erase the report the
+  moment it became explicable — the faint tier is how the display says "this was missing but arrived
+  late". `RowSet` sends one `plot::InvalidSpan` per hole to every row — a gap is in the stream, not
+  in one signal — and only in `Live` and `Capturing`, because a `Held` or `Paused` snapshot carries
+  its own stamps that the live hole table does not address.
+
 - **`RowSet::signal_color()` is the only route to a trace's colour.** The user can override the
   palette entry per signal (clicking its chip; `set_signal_color()` / `clear_signal_color()`,
   keyed by **name**, because a palette index is positional and a CONFIG renumbers), and that