docs: update project-level config discovery documentation

- Add project-level config discovery section to terraphim_config summary
- Update main summary.md with new ProjectConfig type and discovery feature
- Add release announcement to .docs/releases/v2026.05.19.md

Refs: project config discovery feature (commits 59cd233, 26f5b87)

Author: Alex

.docs/summary-crates-terraphim_config-src-lib.rs.md

@@ -7,6 +7,13 @@
 2. Saved config retrieved from persistence layer
 3. Hard-coded defaults in `terraphim_server/default/`
 
+**Project-Level Config Discovery:**
+- Searches parent directories for `.terraphim/` directory starting from current working directory
+- Enables project-specific roles, global shortcuts, and configuration overrides
+- Merged with global config via `Config::with_project()` and `Config::merge_with()`
+- Roles merged by `RoleName`: project role fully replaces global role (no deep merge)
+- `global_shortcut` field is optional in project configs
+
 **Key Types:**
 - **`Config`**: Top-level configuration holding all roles, global shortcut, default/selected role
 - **`Role`**: User profile with haystacks, relevance function, theme, LLM settings

.docs/summary.md

@@ -97,6 +97,14 @@ User Query
 - `Role`: User profile with haystacks, relevance function, theme, LLM settings
 - `Haystack`: Data source descriptor with service type
 - `KnowledgeGraph`: Automata path and/or local KG files
+- `ProjectConfig`: Project-level overrides in `.terraphim/config.json`
+
+**Project-Level Config Discovery:**
+- Searches parent directories for `.terraphim/` directory starting from CWD
+- Enables project-specific roles, global shortcuts, and configuration overrides
+- Merged with global config via `Config::with_project()` and `Config::merge_with()`
+- Roles merged by `RoleName`: project role fully replaces global role
+- Optional `global_shortcut` field allows project configs to omit it
 
 **Service Types Supported:**
 - Ripgrep, Atomic Server, QueryRs, ClickUp, MCP, Perplexity, GrepApp, AiAssistant, Quickwit, JMAP