Remove unreachable utility functions

Several small utility functions are unreachable:

Files to clean:
1. `internal/storage/sqlite/hash.go` - `computeIssueContentHash` (line 17)
   - Check if entire file can be deleted if only contains this function

2. `internal/config/config.go` - `FileUsed` (line 151)
   - Delete unused config helper

3. `cmd/bd/git_sync_test.go` - `verifyIssueOpen` (line 300)
   - Delete dead test helper

4. `internal/compact/haiku.go` - `HaikuClient.SummarizeTier2` (line 81)
   - Tier 2 summarization not implemented
   - Options: implement feature OR delete method

Impact: Removes 50-100 LOC depending on decisions

- Remove unreachable functions
- If entire files can be deleted (like hash.go), delete them
- For SummarizeTier2: decide to implement or delete, document decision
- All tests pass: `go test ./...`
- Verify no callers exist for each function


Remove unreachable RPC methods

Several RPC server and client methods are unreachable and should be removed:

Server methods (internal/rpc/server.go):
- `Server.GetLastImportTime` (line 2116)
- `Server.SetLastImportTime` (line 2123)
- `Server.findJSONLPath` (line 2255)

Client methods (internal/rpc/client.go):
- `Client.Import` (line 311) - RPC import not used (daemon uses autoimport)

Evidence:
```bash
go run golang.org/x/tools/cmd/deadcode@latest -test ./...
```

Impact: Removes ~80 LOC of unused RPC code

- Remove the 4 unreachable methods (~80 LOC total)
- Verify no callers: `grep -r "GetLastImportTime\|SetLastImportTime\|findJSONLPath" .`
- All tests pass: `go test ./internal/rpc/...`
- Daemon functionality works: test daemon start/stop/operations


Refactor sqlite.go (2298 lines)

Break down internal/storage/sqlite/sqlite.go into smaller, more focused modules. The file is currently 2298 lines and should be split into logical components.


Wrap git operations in GitClient interface

Create internal/daemonrunner/git.go with GitClient interface (HasUpstream, HasChanges, Commit, Push, Pull). Default implementation using os/exec. Use in Syncer and Run loop for testability.


Document bd edit command and verify MCP exclusion

Follow-up from PR #152:
1. Add "bd edit" to AGENTS.md with "Humans only" note
2. Verify MCP server doesn't expose bd edit command
3. Consider adding test for command registration