re: kill the duplicate-resource-name hypothesis for the viewer bug, and reconcile 22 vs 16 stages

build_ship_model resolves each placement with find(|m| m.name == p.resource) --
first match wins -- so a repeated resource name inside a container would draw
the wrong geometry. It cannot happen: decoding every XBG7 resource in all 22
stage containers gives 4603 resources and ZERO repeated names. Per ship it is
tighter still: e106 wants 9 distinct names and decodes exactly 9 models for 11
placements, e105 9 for 9, f105 5 for 6.

Two of the three remaining candidates for the user-reported viewer bug are now
gone (this and include_external), leaving mirror handling and the exhaust cones,
plus the untried visual comparison.

The container sweep also reconciles a number I flagged earlier: the disc has 22
stage CONTAINERS -- Stage_S01..S16 plus Stage_S24..S29 -- i.e. 16 story stages
plus 6 extra. The save screen's 16 STAGE sprites and the notes' "22 stages" are
both right and count different things; neither gets edited to match the other.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/re/BACKLOG.md

@@ -81,3 +81,35 @@ a resource name repeats, and the exhaust cones. **Next step is a visual**: the
 diagnosis has run out of things it can settle by reading, so the viewer needs to
 be run against a known-good class (`e106`) and its render compared with
 `ship_render`'s.
+
+---
+
+## Viewer: the duplicate-resource-name hypothesis is dead too
+
+**Checked 2026-08-11.** The diagnosis above left three candidates for why capital
+ships assemble wrong in the viewer: mirror handling, `Xbg7Model::models_named`
+resolving the wrong sub-model when a resource name repeats, and the exhaust
+cones. The second is now **refuted**, and comprehensively.
+
+`build_ship_model` resolves each placement with
+`base.iter().find(|m| m.name == p.resource)` (`iso_loader.rs:4041`) — first match
+wins — so a repeated resource name inside a container would silently draw the
+wrong geometry. It cannot happen: decoding **every** XBG7 resource in **all 22
+stage containers** gives **4 603 resources and zero repeated names**.
+
+```
+Stage_S01  62/62      Stage_S07 323/323     Stage_S13 290/290     Stage_S25 351/351
+Stage_S02 304/304     Stage_S08 388/388     Stage_S14  22/22      Stage_S26 318/318
+Stage_S03 214/214     Stage_S09 316/316     Stage_S15 386/386     Stage_S27 321/321
+Stage_S04 179/179     Stage_S10   7/7       Stage_S16  65/65      Stage_S28 118/118
+Stage_S05  92/92      Stage_S11 157/157     Stage_S24 162/162     Stage_S29 386/386
+Stage_S06 266/266     Stage_S12 376/376
+```
+
+Per-ship it is tighter still: `e106` wants 9 distinct names and decodes exactly
+9 models for 11 placements; `e105` 9 for 9; `f105` 5 for 6. Every placement
+resolves to the one model it names.
+
+**So two of the three candidates are gone** (this one and `include_external`),
+leaving **mirror handling** and **the exhaust cones** — and the still-untried
+visual comparison, which remains the right next step.

docs/re/structures/savegame-format.md

@@ -448,9 +448,11 @@ Three things fall out, none of which needed the emulator:
   shows as `At Standby`), `STATE_STAGE_CLEAR`, `STATE_GAME_CLEAR`.
 - **The screen can label exactly 16 stages**, `STAGE01`…`STAGE16`. That matches
   `weapon.tbl`'s `AUTO_SETTINGS` list — `stage01…16` plus `tutorial01…06` and
-  `challenge01…06` — so **16 is the story-stage count**, and the "22 stages"
+  `challenge01…06` — so **16 is the story-stage count**. ✅ **The "22 stages"
-  figure used elsewhere in these notes counts a different set (🟡 probably story
+  figure used elsewhere in these notes is now reconciled**: the disc carries 22
-  plus challenge). Worth reconciling before either number is relied on.
+  stage *containers*, `Stage_S01…S16` **plus `Stage_S24…S29`** — 16 story + 6
+  extra. Both numbers are right; they count different things, and neither should
+  be edited to match the other.
 
 The panel's own field names are here too, with their screen positions:
 `Points`, `FlightTime` (`%03d:%02d:%02d`), `ClearTimes`, `CompletionRate`,