docs(repo): remove orphaned pre-re-scope images/ folder (closes #113)

[yinsong1986]

What changed

Removes the orphaned root images/ folder (~380 KB) and updates NOTICE
to match.

Deleted:

• images/architecture_overview.png
• images/how_it_works_flow.png
• images/libero_example.mp4

Edited:

• NOTICE — the "Images and Media" stanza explicitly listed the three
  deleted files. Replaced it with the current originals (docs/assets/strands-logo.svg
  plus the inline Mermaid diagrams) so attribution stays accurate.

Why

These assets were outdated and orphaned:

• Unreferenced. Nothing in README.md, docs/, or examples/
  pointed at them. The only references in the tree were the now-deleted
  NOTICE lines (handled here). The examples/* matches for
  libero_example refer to the deleted Python file
  examples/libero_example.py, not these image assets.
• Stale. Untouched since the initial commit (44b5aab, 2026-02-04),
  predating the Isaac-only re-scope (Umbrella: re-scope robots-sim as the heavy NVIDIA simulation backends for strands-robots #8), the README/docs rewrite (R25: Documentation site (MkDocs Material + GitHub Pages) + README rewrite, mirroring strands-labs/robots (Isaac-only) #72),
  and the MkDocs site.
• Superseded. Current architecture/flow visuals are rendered inline
  as Mermaid diagrams in docs/index.md ("How it works") and
  docs/architecture.md. The docs site has its own current assets under
  docs/assets/. The PNGs/MP4 depict the pre-re-scope design (legacy
  SimEnv; libero_example.mp4 is an old MuJoCo-era demo) and don't
  reflect today's Isaac-Sim-plugin architecture.

Test surface

• hatch run lint — passes (black, isort, flake8).
• hatch run test — 203 passed, 33 skipped. No new failures.

This is an asset/attribution-only change; no Python source paths touched.

Acceptance criteria

• No orphaned, pre-re-scope image assets remain at the repo root.
• Any retained visual reflects the current Isaac-Sim-plugin
  architecture and is referenced by the README/docs — the Mermaid
  diagrams in docs/index.md + docs/architecture.md already cover the
  architecture/flow visuals; no new static image was introduced.

Out-of-scope follow-ups

• None. The issue offered an alternative (regenerate an Isaac-only hero
  image and reference it from the README); we took the smaller correct
  path (removal) since the Mermaid diagrams already cover the visuals.

Closes #113.

Project board: please move #113 to "In review" (board:
Strands Labs - Robots).