Preserve Tier2 selector-byte source evidence

docs/rehost-queue.md

@@ -16,10 +16,12 @@ This file is the short active queue for the current runtime and reverse-engineer
 - Keep the next static Tier-2 building pass focused on the earlier seed/projection seam into `0x00412d70`, not another broad `BuildingTypes` sweep.
   The grounded owner strip is `0x004196c0 -> 0x00414490 -> 0x00416ce0 -> 0x00419230`, and the checked candidate-table export now keeps the concrete row families explicit too: among the `37` probe-bearing maps, `Port00/Warehouse00` stay at `35/43` on `30` maps and shift earlier to `10/18` on `7`, while `Port01..11` / `Warehouse01..11` stay fixed at `45..55` / `56..66` and the numbered trailer family splits independently at `0x00000001 -> 28 maps` versus `0x00000000 -> 9 maps`. The active open question is therefore which earlier seed/projection path lets that fixed numbered cluster reach `0x00412d70` with nonzero `[candidate+0xba/+0xbb]` before `0x00419230` clones or renames it.
   Preserved checked row-family detail now lives in [Tier2 candidate row families](rehost-queue/tier2-candidate-row-families-2026-04-21.md).
+  Preserved checked stock selector-byte detail now lives in [Tier2 selector-byte sources](rehost-queue/tier2-selector-byte-sources-2026-04-21.md).
 
 ## Preserved Detail
 
 - [Archive snapshot](rehost-queue/archive-2026-04-19.md)
 - [Periodic company control lane](rehost-queue/periodic-company-control-lane-2026-04-21.md)
 - [Tier2 candidate row families](rehost-queue/tier2-candidate-row-families-2026-04-21.md)
+- [Tier2 selector-byte sources](rehost-queue/tier2-selector-byte-sources-2026-04-21.md)
 - [Progress history](history/progress-history.md)

docs/rehost-queue/README.md

@@ -8,3 +8,5 @@ useful as evidence, but should not stay in the short active queue file.
   for the active periodic-company queue head.
 - `tier2-candidate-row-families-2026-04-21.md`: checked candidate-table row-family split for the
   active Tier-2 `0x00412d70` queue head.
+- `tier2-selector-byte-sources-2026-04-21.md`: checked stock `BuildingTypes` selector-byte and
+  alias-root evidence for the active Tier-2 `0x00412d70` queue head.

docs/rehost-queue/tier2-selector-byte-sources-2026-04-21.md

@@ -0,0 +1,65 @@
+# Tier2 Selector-Byte Sources (2026-04-21)
+
+This note preserves the stock selector-byte evidence behind the current Tier-2 queue head, so the
+short queue does not have to restate the `BuildingTypes` side every time.
+
+## Checked Export
+
+- `artifacts/exports/rt3-1.06/building-type-sources.json`
+
+## Stock `.bca` Selector Bytes
+
+The checked export keeps the raw `0xb8..0xbb` selector-byte window explicit for every `.bca` file:
+
+- `bca_file_count = 77`
+- `bca_selector_pattern_count = 8`
+- only one checked `.bca` pattern is nonzero at all:
+  - `MachineShop.bca`
+  - `byte_0xb8 = 0x00`
+  - `byte_0xb9 = 0x80`
+  - `byte_0xba = 0x3f`
+  - `byte_0xbb = 0x00`
+
+Everything else in the shipped `.bca` selector-byte corpus stays zero at `0xb8..0xbb`.
+
+## Nonzero `.bty` Alias Family
+
+The checked recovered-table summaries keep the nonzero `.bty` alias family explicit too:
+
+- `nonzero_bty_header_alias_selector_summaries`
+  - `17` grouped selector summaries
+  - `22` files total
+- the strongest same-root family is the `TextileMill` alias-root group:
+  - `dword_0xbb = 0x000001f4`
+  - `byte_0xba = 0x00`
+  - `byte_0xbb = 0x00`
+  - `9` files
+  - sample files include `Port.bty`, `Warehouse.bty`, `ConcretePlant.bty`,
+    `ConstructionFirm.bty`, and `ElectronicsPlant.bty`
+
+The next smaller nonzero alias-root groups are:
+
+- `LumberMill`
+  - `4` files
+- `MeatPackingPlant`
+  - `4` files
+- `Distillery`
+  - `2` files
+- `Toolndie`
+  - `2` files
+
+## Immediate Reading
+
+This keeps the Tier-2 source side narrower than a generic “stock assets might hide selector bytes”
+claim:
+
+- the shipped `.bca` selector-byte corpus is almost entirely zero
+- the one checked nonzero `.bca` outlier is `MachineShop.bca`
+- the broader stock-side nonzero signal sits instead in the `.bty` alias-root family with
+  `dword_0xbb = 0x000001f4`, especially the `TextileMill` branch that already covers `Port.bty`
+  and `Warehouse.bty`
+
+So the remaining Tier-2 question is still not “do the stock source files carry any selector-byte
+signal at all?” It is which earlier seed or projection seam lifts that narrow stock-side signal
+into the live candidate bank bytes `[candidate+0xba/+0xbb]` before `0x00412d70` and
+`0x00419230` consume it.