CI's golangci-lint (v2.12.2) job was failing with 14 issues, which blocked
the dependent test job. This addresses all of them:
- goconst: extract repeated string literals into constants
- format aliases ("md", "word", "htm") in the exporter factory
- "section" lesson type shared by markdown and HTML exporters
- default Articulate Rise base URL and host in the parser
- reuse existing itemType* constants in the markdown switch
- staticcheck (QF1012): replace buf.WriteString(fmt.Sprintf(...)) with
fmt.Fprintf(...) in the markdown exporter
Also drop the hardcoded `go: "1.24"` from .golangci.yml so the target Go
version is autodetected from go.mod.
Replaces the manual string-building implementation of the HTML exporter with a more robust and maintainable solution using Go's `html/template` package. This improves readability, security, and separation of concerns.
- HTML structure and CSS styles are moved into their own files and embedded into the binary using `go:embed`.
- A new data preparation layer adapts the course model for the template, simplifying rendering logic.
- Tests are updated to reflect the new implementation, removing obsolete test cases for the old string-building methods.
Additionally, this commit:
- Adds an `AGENTS.md` file with development and contribution guidelines.
- Updates `.golangci.yml` to allow standard Go patterns for interface package naming.
kjanat