feat(claude): seed curated CLAUDE.md files into ~/dev/ workspace

Adds the omnixy-pattern out-of-store-symlink wiring so consumers can
opt into Claude Code orientation without copying anything by hand.
Files live in lnbits-sensei (so they evolve via PR), symlinks point
back at the consumer's checkout (so edits take effect on the next
Claude session without a nixos-rebuild).

New files under files/:

- dev-CLAUDE.md — generic workspace orientation. Workspace layout,
  quick command set, pointers to docs/. Opt-in (clobbers an existing
  ~/dev/CLAUDE.md, so off by default).
- lnbits-CLAUDE.md — per-project orientation for the lnbits worktree
  subtree. Inline summary of the four most-stepped-on gotchas
  (settings precedence, Quasar UMD self-closing rule, auth-decorator
  distinctions, upstream PR target = `dev` not `main`) plus pointers
  to the docs/ for full reference.

New options under lnbits-sensei.devEnv:

- scaffoldPath — absolute path to the consumer's lnbits-sensei
  checkout. types.str (not types.path) intentionally: types.path
  would copy the file into the Nix store and defeat
  mkOutOfStoreSymlink. Required when any claude.* flag is on.
- claude.enable — seeds ~/dev/lnbits/CLAUDE.md.
- claude.workspaceOrientation — additionally seeds ~/dev/CLAUDE.md.

Wiring lives in home.nix (gated via `osConfig.lnbits-sensei.devEnv.*`)
rather than the dev-env NixOS module, since the file destinations are
under home-manager's purview and the home-manager scope is where
`mkOutOfStoreSymlink` is in scope.

`nix flake check` stays green — `optionalAttrs` is lazy, so
`scaffoldPath` isn't accessed when claude.{enable,workspaceOrientation}
are both false (their defaults).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

files/dev-CLAUDE.md

@@ -0,0 +1,61 @@
+# `~/dev` — lnbits dev workspace
+
+You're working in a dev workspace bootstrapped by **lnbits-sensei**.
+This file is workspace-level orientation; per-project CLAUDE.md files
+(e.g. `~/dev/lnbits/CLAUDE.md`) layer project-specific gotchas on top.
+
+> This file is a symlink into your lnbits-sensei checkout's
+> `files/dev-CLAUDE.md` (via home-manager's `mkOutOfStoreSymlink`).
+> Edits should happen in the checkout and be committed there.
+
+## Layout
+
+```
+~/dev/
+├── repos/                      # bare git repos, one per project
+├── <project>/<worktree>/       # worktrees per branch
+├── upstream-prs/<topic>/       # PR branches against upstreams
+├── shared/, scratch/           # workspace utilities
+└── refs/                       # curated reference repos (optional)
+```
+
+Rationale: bare-repos + per-project-worktree directories means one git
+object database per project (no clone-per-branch churn) and an explicit
+PR contract in `upstream-prs/`. See the lnbits-sensei README's
+"Workspace layout" section for the full reasoning.
+
+## Quick commands
+
+- `dev up [--fakewallet|--regtest]` — start the lnbits dev server.
+  Default `--fakewallet` is instant, no docker, good for
+  extension/UI/API work.
+- `dev down` / `dev logs` / `dev shell` — control / inspect.
+- *(planned)* `prb <repo> <branch>` — create a PR worktree branched
+  from `upstream/main` under `~/dev/upstream-prs/`.
+- *(planned)* `lb <worktree>` — cd shortcut into `~/dev/lnbits/<worktree>`.
+
+## Reference docs
+
+Full reference lives in the lnbits-sensei checkout's `docs/`:
+
+- `docs/remotes.md` — three remote-topology patterns (upstream-only /
+  github-fork / multi-remote-with-private).
+- `docs/upstream-prs.md` — PR workflow with a primer for anyone new
+  to fork-based contribution.
+- `docs/lnbits-upstream-flow.md` — how `lnbits/lnbits` itself moves
+  (the `dev` / `main` branch split, squash-merge convention).
+- `docs/lnbits-workspace-notes.md` — practical gotchas: port choice,
+  `LNBITS_SRC` build-context traps, extension-folder-upgrade wiping
+  forks, Nostr key handling, CLINK scope, fork versioning, **settings
+  precedence (`.env` vs DB)**.
+
+## Per-project orientations
+
+Per-project CLAUDE.md files are placed at the worktree root:
+
+- `~/dev/lnbits/CLAUDE.md` — LNbits dev gotchas (settings precedence,
+  frontend rules, auth decorators, …).
+
+These are also symlinked from your lnbits-sensei checkout (under
+`files/`); the seeding is driven by `lnbits-sensei.devEnv.claude.*`
+options.