docs(discovery): map L1 packages vs standalone php-* modules (#3)

Adds discovery document summarising all Boot.php locations under
src/Core/, their relationship to standalone core/php-* repos, and
the three overlaps identified (issues #4, #5, #6). Full summary
filed as issue #7.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/discovery/l1-packages-vs-standalone-modules.md

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+# Discovery: L1 Packages vs Standalone php-* Modules
+
+**Issue:** #3
+**Date:** 2026-02-21
+**Status:** Complete – findings filed as issues #4, #5, #6, #7
+
+## L1 Packages (Boot.php files under src/Core/)
+
+| Package | Path | Has Standalone? |
+|---------|------|----------------|
+| Activity | `src/Core/Activity/` | No |
+| Bouncer | `src/Core/Bouncer/` | No |
+| Bouncer/Gate | `src/Core/Bouncer/Gate/` | No |
+| Cdn | `src/Core/Cdn/` | No |
+| Config | `src/Core/Config/` | No |
+| Console | `src/Core/Console/` | No |
+| Front | `src/Core/Front/` | No (root) |
+| Front/Admin | `src/Core/Front/Admin/` | Partial – `core/php-admin` extends |
+| Front/Api | `src/Core/Front/Api/` | Partial – `core/php-api` extends |
+| Front/Cli | `src/Core/Front/Cli/` | No |
+| Front/Client | `src/Core/Front/Client/` | No |
+| Front/Components | `src/Core/Front/Components/` | No |
+| Front/Mcp | `src/Core/Front/Mcp/` | Intentional – `core/php-mcp` fills |
+| Front/Stdio | `src/Core/Front/Stdio/` | No |
+| Front/Web | `src/Core/Front/Web/` | No |
+| Headers | `src/Core/Headers/` | No |
+| Helpers | `src/Core/Helpers/` | No |
+| Lang | `src/Core/Lang/` | No |
+| Mail | `src/Core/Mail/` | No |
+| Media | `src/Core/Media/` | No |
+| Search | `src/Core/Search/` | No (admin search is separate concern) |
+| Seo | `src/Core/Seo/` | No |
+
+## Standalone Repos
+
+| Repo | Package | Namespace | Relationship |
+|------|---------|-----------|-------------|
+| `core/php-tenant` | `host-uk/core-tenant` | `Core\Tenant\` | Extension |
+| `core/php-admin` | `host-uk/core-admin` | `Core\Admin\` | Extends Front/Admin |
+| `core/php-api` | `host-uk/core-api` | `Core\Api\` | Extends Front/Api |
+| `core/php-content` | `host-uk/core-content` | `Core\Mod\Content\` | Extension |
+| `core/php-commerce` | `host-uk/core-commerce` | `Core\Mod\Commerce\` | Extension |
+| `core/php-agentic` | `host-uk/core-agentic` | `Core\Mod\Agentic\` | Extension |
+| `core/php-mcp` | `host-uk/core-mcp` | `Core\Mcp\` | Fills Front/Mcp shell |
+| `core/php-developer` | `host-uk/core-developer` | `Core\Developer\` | Extension (also needs core-admin) |
+| `core/php-devops` | *(DevOps tooling)* | N/A | Not a PHP module |
+
+## Overlaps Found
+
+See issues filed:
+
+- **#4** `Front/Api` rate limiting vs `core/php-api` `RateLimitApi` middleware – double rate limiting risk
+- **#5** `Core\Search` vs `core/php-admin` search subsystem – dual registries
+- **#6** `Core\Activity` UI duplicated in `core/php-admin` and `core/php-developer`
+- **#7** Summary issue with full analysis