feat: architecture.svg as README hero (replacing planned hero.gif)

Per Hector's call: skip hero gif (4-6 hr work), use a polished
static architecture diagram instead. Diagram shows the full flow:
plan -> 3 LLMs in parallel -> consolidate -> ranked findings,
with the "Unique (1 team)" category highlighted as where the value
compounds.

Bottom byline reinforces the no-install positioning: "no install ·
no plugin · ~30 lines in your CLAUDE.md".

Saved to assets/architecture.svg (planned location per plan v3
file structure). Both README.md and README.zh-TW.md now reference
it instead of the un-recorded hero.gif.

Author: hectorhuang0830

README.md

@@ -17,7 +17,7 @@
 
 [中文 README](./README.zh-TW.md) · [Methodology](./docs/methodology.md) · [Course outline](#course-outline)
 
-![demo](./assets/hero.gif)
+![architecture](./assets/architecture.svg)
 
 ## Three ways to run it. None require an install of this repo.
 

README.zh-TW.md

@@ -12,7 +12,7 @@
 
 [English README](./README.md) · [方法論](./docs/methodology.zh-TW.md) · [章節索引](#章節索引)
 
-![demo](./assets/hero.gif)
+![architecture](./assets/architecture.svg)
 
 ## 三種跑法，都不用安裝這個 repo