docs(sdk): clarify pluginRoot scope for runtime plugins — #285 (activation-context: ActivateContext n'expose ni répertoire d'installation ni racine package ni file URL; commands-and-feedback + services: runCommand project/workspace-scoped, aucune résolution package-relative des scripts packagés; manifest: substitution ${pluginRoot}/${appDataDir} étendue par l'hôte uniquement dans contributes.mcpServers command/args/env/cwd; QA verte: npm run build, cohérence champs vs types SDK vérifiée)

docs/manifest.md

@@ -247,6 +247,18 @@ Contribution ids are part of the runtime contract:
 - `services.windows.open({ layoutType })` only accepts a layout type declared by
   the calling plugin.
 
+## MCP Server Paths
+
+`contributes.mcpServers` entries are resolved by the host before starting a
+declared MCP server. In `command`, `args`, `env` and `cwd`, the host expands:
+
+- `${pluginRoot}` to the installed plugin package root.
+- `${appDataDir}` to the host-owned application data directory.
+
+This substitution is limited to manifest-declared MCP server startup. It is not
+available from `activate(ctx)`, `ctx.services.workspace` or
+`ctx.services.tasks.runCommand()`.
+
 ## Validation
 
 Use the SDK validator in tests or build tooling: