Reorganize project into standard root layout

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/copilot-instructions.md

@@ -24,5 +24,5 @@ Always use the Makefile for development tasks. Never run raw `go test`, `go vet`
 
 1. **Before changes**: Run `make check` to establish baseline.
 2. **After changes**: Run `make check` and `make race`.
-3. **Frontend edits**: Run `make build` after changing `go/webterm/static/js/terminal.ts`.
+3. **Frontend edits**: Run `make build` after changing `webterm/static/js/terminal.ts`.
 4. **Major validation**: Run `make build-all` for a reproducible full run.

.github/instructions/go.instructions.md

@@ -7,5 +7,5 @@ Applies when: this repo has `go.mod`.
 - Put `golangci-lint` and `gosec` wiring behind Make targets when introduced.
 
 ## Conventions to implement
-- `make test` should run `cd go && go test ./...`.
+- `make test` should run `go test ./...`.
 - Avoid bespoke CI steps when a Make target can encode the same behavior.