Make research skill self-contained without external scripts

- Rewrite SKILL.md with inline instructions to spawn g3 --agent scout directly
- Extend read_file to handle embedded skill paths (<embedded:name>/SKILL.md)
- Remove scripts field from EmbeddedSkill struct (no longer needed)
- Delete extraction.rs module (was only for script extraction)
- Delete g3-research bash script
- Remove obsolete Async Research Tool section from workspace memory

Skills are now fully portable - they work when g3 is installed as a
binary without access to source files. Agents can read embedded skill
content via read_file with the special <embedded:...> path syntax.

analysis/memory.md

@@ -211,37 +211,6 @@ max_tokens = 4096
 gpu_layers = 99
 ```
 
-### Async Research Tool
-Research tool is asynchronous - spawns scout agent in background, returns immediately with research_id.
-
-- `crates/g3-core/src/pending_research.rs`
-  - `PendingResearchManager` [80..100] - thread-safe task storage (Arc<Mutex<HashMap>>)
-  - `ResearchTask` [40..75] - id, query, status, result, started_at, injected
-  - `ResearchStatus` [20..35] - Pending, Complete, Failed enum
-  - `register()` [110..125] - creates task, returns research_id
-  - `complete()` / `fail()` [130..150] - update task status
-  - `take_completed()` [180..200] - returns completed tasks, marks as injected
-  - `list_all()` [165..170] - returns all tasks for /research command
-
-- `crates/g3-core/src/tools/research.rs`
-  - `execute_research()` [150..210] - spawns scout in tokio::spawn, returns placeholder
-  - `run_scout_agent()` [215..300] - async fn that runs in background task
-  - `execute_research_status()` [305..380] - check status of pending research
-
-- `crates/g3-core/src/lib.rs`
-  - `inject_completed_research()` [1080..1120] - injects completed research into context
-  - Called at start of each tool iteration and before user prompt in interactive mode
-
-- `crates/g3-cli/src/commands.rs`
-  - `/research` command [125..160] - lists all research tasks with status
-
-**Flow:**
-1. Agent calls `research(query)` → returns immediately with research_id
-2. Scout agent runs in background tokio task
-3. On completion, `PendingResearchManager.complete()` stores result
-4. At next iteration start or user prompt, `inject_completed_research()` adds to context
-5. Agent can check status with `research_status` tool or user with `/research` command
-
 ### Plan Mode (replaces TODO system)
 Structured task planning with cognitive forcing - requires happy/negative/boundary checks.