Correct the fleet graph overview for CMMMech and AIMech #400

At PR #399 head 5a866f2e17eab30ff696ed4ebbb6f36ec5d5ec7c, the graph's initial panel says “14 views of one microbe.” Its clockwise description omits CMMMech and AIMech and says the ring closes at culture media, although AIMech follows it.

This misrepresents AIMech's subject and leaves two nodes unexplained. The same text appears at desktop and mobile widths in both themes.

Update overview() in _fleet/fleet_fragment.html to describe fourteen complementary knowledge factories, include critical mineral recovery and AIMech in the actual ring order, and regenerate mechs.md. Verify the rendered default panel in all four viewport/theme combinations.

Priority: P3. Resolution belongs in PR #399.