fix(template): parameterize scaffold with __PROJECT_NAME__/__MODULE_PATH__ (gitea-mcp#44)

template-go-web was seeded from the real `hostexecutor` project and never
parameterized: go.mod hardcoded `module gitea.d-ma.be/mathias/hostexecutor` and
`hostexecutor` appeared throughout (cmd dir, Dockerfile, Taskfile, CI, context
docs). create_project_from_template therefore substituted nothing and returned
a "no placeholders" partial_failure on the zero-config default path.

Replaced the full module path with __MODULE_PATH__ and the bare project name
with __PROJECT_NAME__ (incl. renaming cmd/hostexecutor → cmd/__PROJECT_NAME__),
matching the substitution the tool performs. Also drops the stale gitea.d-ma.be
host (the placeholder resolves to git.d-ma.be/<owner>/<name>).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.context/system-prompt.txt

@@ -3,14 +3,14 @@ Follow all conventions from both the root agent context and project context.
 
 ---
 
-# hostexecutor
+# __PROJECT_NAME__
 
 ## Identity
 
-- **Name**: hostexecutor
+- **Name**: __PROJECT_NAME__
 - **Owner**: Mathias
 - **Client**: personal
-- **Repo**: gitea.d-ma.be/mathias/hostexecutor
+- **Repo**: __MODULE_PATH__
 - **Status**: active
 
 ## Stack