test layout: move shared tests out of `claude-code/tests/` to a root-level `tests/` dir

## Problem

`claude-code/tests/` currently holds **107 test files** — but the overwhelming majority test code that has nothing to do with claude-code specifically:

- Tests for shared `src/` modules (auth, cli, deeplake-api, embeddings, hooks, skillify, notifications, …)
- Tests that exercise **other agents'** bundles (`cursor-session-start-hook.test.ts`, `hermes-session-start-hook.test.ts`, `cli-install-codex-fs.test.ts`, `cli-install-openclaw.test.ts`, etc.)

By contrast, the agent-specific test directories are tiny:
- `codex/tests/` — 4 files (codex hooks + capture integration)
- `openclaw/tests/` — 3 files (auto-recall, hivemind-tools, setup-command)
- `cursor/` / `hermes/` / `pi/` — no `tests/` dir at all; their tests live under `claude-code/tests/`

The root `vitest.config.ts:4-6` already acknowledges the oddity:

> The one in claude-code/ is a historical leftover and is not used by the root test script.

## Proposal

Move shared tests to a root-level `tests/` directory and keep `/tests/` for genuinely agent-specific integration tests.

### Target layout

```
tests/ <- new home for everything that tests shared src/
auth.test.ts
deeplake-api.test.ts
skillify-*.test.ts
embeddings/*.test.ts
...

claude-code/tests/ <- claude-code-specific only
session-start-hook.test.ts (the one that tests CC's own SessionStart bundle)
install-end-to-end.test.ts (if it really only exercises CC)
...

codex/tests/ <- unchanged
cursor/tests/ <- new home for cursor-session-start-hook.test.ts, etc.
hermes/tests/ <- new home for hermes-session-start-hook.test.ts, etc.
openclaw/tests/ <- unchanged
pi/tests/ <- new home for pi-* tests if they exist
```

### Steps

1. `git mv` the ~95 shared-module tests from `claude-code/tests/` to `tests/`
2. `git mv` cursor/hermes hook tests to their respective `/tests/` directories
3. Update import paths in moved tests (`../../src/...` → `../src/...` for `tests/`, stays `../../src/...` for `/tests/`)
4. Update `vitest.config.ts` `include` array:
```ts
include: [
"tests/**/*.test.ts",
"claude-code/tests/**/*.test.ts",
"codex/tests/**/*.test.ts",
"cursor/tests/**/*.test.ts",
"hermes/tests/**/*.test.ts",
"openclaw/tests/**/*.test.ts",
"pi/tests/**/*.test.ts",
],
```
5. Update the stale comment in `vitest.config.ts:4-6`
6. Grep CI workflows for hardcoded `claude-code/tests/` paths and update (`ci.yml` references it in the coverage step)
7. Update the testing-philosophy section in CLAUDE.md that names `claude-code/tests/upload-summary.test.ts` etc. — those paths will change

### Gotchas to handle in the PR

- **Big diff**: ~107 file moves, but mechanical — should be reviewable as a pure rename PR
- **Import paths**: relative `../../src/` becomes `../src/` for files moved to root `tests/`. Codemod-able with `sed -i`
- **Agent boundary judgment calls**: some tests live in `claude-code/tests/` but exercise generic shared code via a claude-code-bundled artifact (e.g. bundle-scan tests). These could go either way — root `tests/` if they cover all-agent invariants, `claude-code/tests/` if specifically about CC's bundle
- **Coverage thresholds in `vitest.config.ts`**: per-file `thresholds` block references `src/**` paths, not test paths — no change needed there
- **Pre-commit hook + lint-staged**: only target `*.ts` globally, unaffected

### Why now / why not later

- **Why now**: skillify code lives under `src/skillify/` (root), gets bundled into every agent, but its tests live under `claude-code/tests/skillify-*.test.ts` — actively confusing for anyone navigating the codebase. The wrong location reinforces the wrong mental model.
- **Why not later**: a refactor PR is cheaper to land in isolation than bundled with a feature change. Every PR that touches a test file under `claude-code/tests/` (i.e. most PRs) postpones this by burying it under reviewer fatigue.

## Out of scope

- Splitting tests by domain (`tests/auth/`, `tests/skillify/`, etc.) — possible follow-up; this issue just gets the wrong-named container fixed first.
- Migrating coverage thresholds — they key on `src/**`, unaffected.