chore: move Delta Command to its own repository

[nfaggian]

Summary

Delta Command (the engineering ops dashboard under apps/delta-command/) has outgrown its home in agent-experiments and is being moved to its own repository, nfaggian/delta-tools.

This PR performs the "remove from source" half of the move:

• Deletes apps/delta-command/ — 52 files, ~10,100 lines
• Adds a one-line breadcrumb at the top of the root README pointing to the new repo

The other half — pushing to nfaggian/delta-tools

Since Cloud Agents can't create new GitHub repositories, the export half has been done as a companion branch you can push to a brand-new repo once you create it.

Branch: cursor/delta-tools-export-535c

• Produced with git subtree split --prefix=apps/delta-command HEAD from the tip of cursor/llm-briefing-535c (which contains the latest Google branding, simplification, LLM briefing, and minimal UI work).
• 20 commits of delta-command history preserved, paths rewritten so every file that lived at apps/delta-command/foo now lives at foo at the repo root.
• Tree contents verified to match the current apps/delta-command/ exactly.

One-time handoff

Create the delta-tools repository on GitHub (empty, no README/license/gitignore), then push the export branch to it:

# 1. Create the repo on GitHub (via UI or `gh repo create nfaggian/delta-tools --public`)

# 2. Clone the export branch from agent-experiments
git clone --branch cursor/delta-tools-export-535c --single-branch \
  https://github.com/nfaggian/agent-experiments.git delta-tools
cd delta-tools

# 3. Repoint origin and push as main
git remote set-url origin https://github.com/nfaggian/delta-tools.git
git branch -M main
git push -u origin main

nfaggian/delta-tools will land with:

• The full delta-command project rooted at the top level (backend/, src/, package.json, tailwind.config.ts, both READMEs, etc.).
• 20 commits of history — every notable milestone (initial hub, YAML→JSON migration, dark mode, 30-engineer scaling, simplification pass, LLM briefing, minimal UI pass).
• Working uv run pytest and npm run build out of the box (they only depend on paths inside the subtree, verified during earlier work).

After the export lands

• Close the sibling draft PRs on this repo (#8 simplify, #9 LLM briefing + minimal UI) — their contents are already part of the export branch and will be committed to delta-tools.
• Delete the cursor/delta-tools-export-535c branch from agent-experiments once it has been pushed to delta-tools (it's only meant as a shipping vehicle).

Verification

• apps/delta-command/ is fully self-contained: no imports from repo root, no references in the root Makefile, pyproject.toml, README.md, or .gitignore. Confirmed by rg "delta[-_]command|apps/delta" returning matches only inside apps/delta-command/.
• Export branch tree exactly matches the current apps/delta-command/ tree (diff -q on git ls-tree -r --name-only output returned no differences).
• apps/ becomes empty after this removal — git will not track the empty parent, so apps/ simply disappears from the repo.