chore: rename to ai-dev-tools

"awesome-coding-agents" no longer described the contents once the scope
widened past coding agents to AI-powered developer tools generally. Renaming
now was near-free: 3 stars, 4 forks, 135 unique visitors, four months old.

Name selection avoided the crowded awesome-* namespace, where the obvious
candidates are held by established lists (awesome-ai-devtools 3.9k,
awesome-ai-tools 6.2k, awesome-ai-coding-tools 2.1k). "ai-dev-tools" has no
incumbent at the exact name.

- Repo renamed; GitHub description and homepage updated.
- Module path, User-Agent, .gitignore, H1, site <title>/og:title and every
  GitHub Pages URL updated across README.md, templates/readme.tmpl,
  docs/LOCAL_DEV.md and site/index.html.
- plans/reports/ left untouched: it is a dated historical record.

go build: ok. go run . -check: 43 agents valid. go test ./...: ok.

go.mod

@@ -1,4 +1,4 @@
-module github.com/tiennm99/awesome-coding-agents
+module github.com/tiennm99/ai-dev-tools
 
 go 1.23