feat(redstone-link): real block textures via build-textures.py, add build.sh

The first textures were a motif floating on a flat slab. That hits the
lesson already documented on mailbox_block(): an icon-like sprite "reads
as a placeholder when applied to all 6 faces of a cube". Replaced with
machine faces whose traces run out to the edges, so they connect across
tile boundaries and a wall of them reads as continuous circuitry --
transmitter radiating out, receiver feeding in.

Generated through scripts/build-textures.py using the existing palette and
rect/px/save helpers rather than an ad-hoc script, so they regenerate with
everything else. Running the pipeline also rewrites the other five
textures, but pixel-identically -- that churn is only a newer Pillow
re-encoding, so those files are left alone.

RP header bumped to 1.0.1 (with the BP dependency to match) because clients
cache packs by uuid+version and would otherwise keep serving the old art.
The lobby world pin was updated to match; a mismatch silently drops the
pack from the stack.

Adds build.sh to package the .mcaddon, mirroring addon/build.sh. It omits
that script's `-x` exclude: these packs have no dotfiles, and dropping it
keeps the script working with the 7-Zip `zip` shim on the workstation as
well as Info-ZIP on the CI runner.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015Gf1kZypRDfPL1YiWUS1LC

redstone-link-addon/redstone_link_RP/manifest.json

@@ -4,7 +4,7 @@
     "name": "Redstone Link Resources",
     "description": "Textures and lang for the silverlabs:redstone_link_tx / _rx blocks",
     "uuid": "e4f1a7c2-6b95-4d38-a7e0-3c81d5f2b004",
-    "version": [1, 0, 0],
+    "version": [1, 0, 1],
     "min_engine_version": [1, 21, 0]
   },
   "modules": [