Add a Troubleshooting section to apps/identity-wallet/CLAUDE.md covering
all five error classes encountered when running cargo tauri ios dev in the
Nix devenv: missing iOS stdlib, simctl not found, -mmacos-version-min
conflict, libiconv not found, and UIKit framework not found.

Also document:
- cargo tauri ios dev must orchestrate the build (not Xcode's Run button)
- nix develop must be run from workspace root
- src-tauri/.cargo/config.toml and why it exists

Update root CLAUDE.md to reflect the switch from languages.rust to rustup
and document DEVELOPER_DIR re-export.

Four interacting issues prevented `cargo tauri ios dev` from working in the
Nix devenv environment:

1. languages.rust used Nix's rust-default which ships no iOS target stdlibs.
Fix: replace with pkgs.rustup + project-local RUSTUP_HOME/CARGO_HOME so
rustup reads rust-toolchain.toml and installs aarch64-apple-ios-sim stdlib.

2. Nix Darwin setup hooks override DEVELOPER_DIR to a stub apple-sdk with no
runtime tools (xcrun simctl fails with "tool not found").
Fix: re-export DEVELOPER_DIR to real Xcode.app in enterShell, which runs
after all Nix hooks and wins.

3. Nix cc-wrapper injects -mmacos-version-min into iOS target CC invocations,
which clang rejects alongside -mios-simulator-version-min.
Fix: src-tauri/.cargo/config.toml sets CC_aarch64_apple_ios_sim to
Xcode's unwrapped clang for build scripts.

4. Nix cc-wrapper uses macOS sysroot for the iOS target final link, failing to
find UIKit and other iOS frameworks.
Fix: .cargo/config.toml sets [target.aarch64-apple-ios-sim].linker (and
aarch64-apple-darwin for proc-macro host builds) to Xcode's clang.

- Remove security.csp=null from tauri.conf.json — restores Tauri's
restrictive default CSP (critical for an identity wallet)
- Fix package.json version 0.0.1 → 0.1.0 to match workspace/tauri.conf
- Fix vite.config.ts host fallback '0.0.0.0' → 'localhost' so standalone
pnpm dev does not expose the dev server to the LAN
- Add #[cfg(test)] block to lib.rs with 3 greet tests (normal, empty,
special chars) establishing the testing pattern for src-tauri
- Commit docs/implementation-plans/2026-03-14-MM-143/ (was untracked)

The flake.nix buildDepsOnly call is scoped to relay-related crates to
avoid compiling Tauri's native dependencies in Nix. This boundary is
important for future workspace additions and belongs in CLAUDE.md.