docs: define the status markers, and fix six mislabelled or superseded entries

An audit of BACKLOG.md turned up a class of error with a single root cause: the
README defines only the CONFIRMED/PROBABLE/HYPOTHESIS confidence scale, while
the pages actually use a second vocabulary -- and 🔴 appears 98 times without
ever being defined.  It gets used for two different things, "refuted" and
"blocked", and three entries slid from one into the other.

README now defines ✅/🟡/❔/🔴/❌/🚧 and states the rule the corpus was missing:
🔴 never means "we have not run it yet".  That is ❔ or 🚧.  Its blocked sense is
only for a real limit of the box -- no push credentials, no hardware Vulkan, a
decision only the user can make -- and since the box can run the emulator,
script input, screenshot and read guest memory, "needs a run" is never blocked.
I made exactly this mistake on the world-unit item earlier today, which is what
prompted looking for others.

Fixed in BACKLOG.md:

  * the elimination test, marked 🔴 UNRUN and in fact run and refuted nine
    lines further down;
  * the frozen capture, marked 🔴 STILL UNRUN and in fact taken eleven lines
    down -- 🔴 wrong twice, since "the freeze did not happen this run" is a
    scheduling outcome and not a refutation;
  * a 🚧 STILL UNRUN item whose stated blocker (the boot-nav bug) is fixed;
  * the objective-counter heading, which asserts 0xbdb59668 as the answer while
    its own first body line refutes that address -- retitled to say what is
    actually solved, the method;
  * the paint-order "third measured permutation" question, answered inside its
    own entry by a third, fourth and fifth screen;
  * the UTF-16 endianness question -- resolved, and it is not a stale comment:
    localization.rs both documents LE and decodes with u16::from_le_bytes, so
    it is a code bug worth filing.

Also fixes the corpus's only dangling link (INDEX.md pointed at
structures/idxd-unnamed-keys.md, never written).

docs/re/README.md

@@ -37,6 +37,28 @@ This mirrors the project method — *measure the oracle, never infer; refute bef
 | `PROBABLE` | Strong single-source inference. | One clean observation, or an unambiguous static read of the disassembly. |
 | `HYPOTHESIS` | Educated guess, not yet tested. | Anything else. Must say what would confirm/refute it. |
 
+### The status markers
+
+The table above is the *confidence* scale. The markers that appear in
+`BACKLOG.md` and the `structures/` pages are a separate, and until now undefined,
+vocabulary. They mean:
+
+| Marker | Meaning |
+|---|---|
+| ✅ | Confirmed — verified against ground truth. |
+| 🟡 | Partial: true as far as it goes, or true under a stated assumption. |
+| ❔ | Open question. Nobody has answered it yet. |
+| 🔴 | **Refuted** — shown false — **or blocked by something the container cannot do.** |
+| ❌ | A specific claim that was tried and failed. Prefer 🔴. |
+| 🚧 | Work started and not finished. |
+
+**🔴 never means "we have not run it yet."** That is ❔ or 🚧. Reserve 🔴's
+"blocked" sense for a real limit of the box — no push credentials, no hardware
+Vulkan (lavapipe only), or a decision only the user can make. The box *can* run
+the emulator, script input, screenshot, read guest memory, and build and test
+Rust, so "needs a run" is never a blocker. This paragraph exists because the
+marker was undefined for 98 uses and three of them were mislabelled that way.
+
 **Promotion requires new evidence, not re-reading the old evidence.** A `HYPOTHESIS` that
 "looks right again" is still a `HYPOTHESIS`. Only an *independent* check promotes it.
 If evidence later contradicts an entry, **demote it and record the contradiction** — do