docs: add /bg inject to README, CLAUDE.md, and CHANGELOG

Update all documentation to reflect the new /bg inject command:
- README: commands table, background tasks section with inject example
- CLAUDE.md: BackgroundPool description, design decisions
- CHANGELOG: inject feature entry under background tasks
- Test count updated to 58 across all docs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: GrapeInTheTree

CHANGELOG.md

@@ -17,9 +17,10 @@ Format based on [Keep a Changelog](https://keepachangelog.com/).
   - Atomic task ID counter prevents millisecond collisions
   - Shutdown-safe: `closed` flag rejects submissions after `CancelAll`, `Wait` ensures goroutine cleanup
   - Completed tasks auto-cleaned after 30 minutes
+  - `/bg inject <id>` — merge completed task results into main session as `/btw` context note (truncated to 4000 runes). Enables "independent analysis → selective context merge" workflow unique to Pocket Claude
 - **GitHub Actions CI** (`.github/workflows/ci.yml`): automated build, vet, gofmt check, test with race detector on push/PR to main
 - **Makefile**: `make build`, `make test`, `make test-race`, `make vet`, `make fmt`, `make fmt-check`, `make ci` (full local pipeline), `make run`, `make clean`
-- **Test Suite**: 57 test cases across 6 packages, all passing with `-race`
+- **Test Suite**: 58 test cases across 6 packages, all passing with `-race`
   - `store`: CRUD, stats, clear, outbox, message age
   - `claude`: stream JSON parsing, permission denials, UTF-8 truncation
   - `project`: add/remove/switch/rename, background executor, usage tracking, persistence across reloads

CLAUDE.md

@@ -23,7 +23,7 @@ Telegram --> Go Bot --> inbox.json --> Worker --> ProjectManager --> claude -p -
 
 - **ProjectManager**: Owns per-project `Executor` instances. Routes all CLI calls to the active project. Persists config to `projects.json`. Switched via `/project` command.
 - **Worker**: Single goroutine, sequential foreground processing from a buffered channel. Prevents concurrent `claude -p` calls on the main session.
-- **BackgroundPool**: Up to 3 concurrent background tasks via `/bg`. Each task gets an ephemeral `Executor` (not stored in Manager). Independent approval flow routed by `bg_` prefix on callback IDs. Atomic counter for unique task IDs. Semaphore-based slot limiting. Shutdown-safe (`closed` flag rejects new submissions after `CancelAll`).
+- **BackgroundPool**: Up to 3 concurrent background tasks via `/bg`. Each task gets an ephemeral `Executor` (not stored in Manager). Independent approval flow routed by `bg_` prefix on callback IDs. Atomic counter for unique task IDs. Semaphore-based slot limiting. Shutdown-safe (`closed` flag rejects new submissions after `CancelAll`). `/bg inject` merges completed results into main session as `/btw` context notes.
 - **Session**: Explicit `--resume <session_id>` tracking per project. Never uses `--continue` (prevents conflicts with Claude Code terminal in same directory).
 - **Permissions**: Two-phase execution. Phase 1: default permissions, check `permission_denials` in JSON output. Phase 2 (if approved): re-run with `--dangerously-skip-permissions`. Markdown fallback on parse errors.
 - **Media**: Photos/documents downloaded from Telegram to `/tmp`, file path passed to Claude CLI for multimodal analysis.
@@ -64,7 +64,7 @@ internal/
 
 ```bash
 make build          # or: go build -o pocket-claude ./cmd/pocket-claude/
-make test           # or: go test ./...           (57 cases)
+make test           # or: go test ./...           (58 cases)
 make test-race      # or: go test -race ./...     (with race detector)
 make vet            # or: go vet ./...
 make fmt            # or: gofmt -w .
@@ -93,7 +93,7 @@ Messages older than `MESSAGE_TTL_MINUTES` → auto `expired`. Prevents stale ret
 Goroutine spawning for callbacks/messages bounded by semaphore (max 10). Falls back to synchronous execution when limit reached.
 
 ### Background tasks (/bg)
-Each background task gets its own ephemeral `Executor` (not stored in Manager's map). This avoids session tracking race conditions between foreground and background. Approval callbacks are routed by ID prefix: `bg_` → BackgroundPool, `msg_` → Worker. Atomic counter (`sync/atomic.Int64`) for task IDs prevents millisecond collisions. `closed` flag prevents new submissions after `CancelAll` during shutdown. Typing indicators run independently per task.
+Each background task gets its own ephemeral `Executor` (not stored in Manager's map). This avoids session tracking race conditions between foreground and background. Approval callbacks are routed by ID prefix: `bg_` → BackgroundPool, `msg_` → Worker. Atomic counter (`sync/atomic.Int64`) for task IDs prevents millisecond collisions. `closed` flag prevents new submissions after `CancelAll` during shutdown. Typing indicators run independently per task. `/bg inject <id>` takes a completed task's `ResultText` and queues it as a `/btw` message into the main session (truncated to 4000 runes). This enables "independent analysis → selective context merge" — a workflow unique to Pocket Claude.
 
 ### Multi-project support
 Each project gets its own `Executor` with independent session, workDir, and addDirs. `ProjectManager` replaces the single executor in the Worker. Projects persist to `projects.json`. Default project auto-created from `CLAUDE_WORK_DIR` on first run. `/project` command for add/remove/switch via inline keyboard. `/project search <keyword>` scans home directory (depth 3) for git repos matching keyword, shows results as inline buttons for one-tap add. Path validation on add (must be existing directory).

README.md

@@ -123,7 +123,7 @@ go build -o pocket-claude ./cmd/pocket-claude/
 ### Test
 
 ```bash
-make test              # run all tests (57 cases)
+make test              # run all tests (58 cases)
 make test-race         # with race detector
 make ci                # full CI pipeline locally (fmt + vet + build + test)
 ```
@@ -177,6 +177,7 @@ retry - Force retry error messages
 | `/bg <message>` | Run task in background (current project) |
 | `/bg <project> <message>` | Run background task in specific project |
 | `/bg status` | Show running background tasks |
+| `/bg inject <id>` | Inject completed result into current session |
 | `/bg cancel <id>` | Cancel a background task |
 | `/cancel` | Cancel the currently processing foreground message |
 | `/usage` | Show API-equivalent cost and message count (per project) |
@@ -318,7 +319,16 @@ When a background task finishes:
 Found 3 potential security issues...
 ```
 
-Background tasks have their own permission flow — if a background task needs approval, you'll see a separate inline keyboard tagged with the task ID, so it won't interfere with foreground approvals.
+**Inject results into your main conversation:**
+```
+/bg inject bg_1710756000123
+  💉 Injected bg_1710756000123 into current session.
+
+You: "Fix issue #3 from that analysis"     <-- Claude knows the context
+Bot: "Fixed the SQL injection in auth.go..."
+```
+
+This "independent analysis → selective context merge" workflow is unique to Pocket Claude. Background tasks have their own permission flow — if a background task needs approval, you'll see a separate inline keyboard tagged with the task ID, so it won't interfere with foreground approvals.
 
 ### Permission System