Add devcontainer-improvements.md with tooling ideas

[Copilot]

Requested braindump of tooling ideas to evolve dev-dots toward a more complete developer environment — no new languages, tools only.

devcontainer-improvements.md — 14 categories, ~60 tools

• Shell & History — atuin, mcfly, navi, tealdeer, direnv, gum, pet
• File System — yazi, broot, duf, dust, xcp
• Text / Data / JSON — yq, miller, gron, fx, visidata, dasel
• Monitoring & Benchmarking — bottom, procs, hyperfine, tokei, lnav, watchexec
• Network & HTTP — xh, httpie, doggo, bandwhich
• Git — git-absorb, git-branchless, onefetch
• Workflow / Task Running — just, act, pre-commit, commitizen
• Security — age, sops, trufflehog, gitleaks
• Docs — glow, frogmouth, pandoc
• Neovim — plugin pre-warming at build time, DAP, conform.nvim, NVIM_APPNAME
• tmux — tpm, tmux-resurrect, tmux-fzf
• Container / Image — multi-arch builds, pinned versions via build-args, HEALTHCHECK, GHCR publish workflow, Renovate
• AI Workflow — aider, fabric, llm, fzf+LLM preview binding
• Observability — py-spy, memray, FlameGraph, angle-grinder

Each entry includes what the tool does and why it fits this container specifically.

Original prompt

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This section details on the original issue you should resolve

<issue_title>identify improvements developer environment container</issue_title>
<issue_description>unexhausted list of ideas to improve the develop experience in this devcontainer. no implementations just a markdown file with all sorts of ideas to improve this container even further for the "ultimate" developer container. Focus on tools not new programming languages, so do not suggest me to use julia or go, but tooling</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes identify improvements developer environment container #49

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