refactor: introduce LintReader interface, decouple linter from sdk/mpr

[retran]

Why

The linter and executor packages import sdk/mpr directly for *mpr.Reader, coupling them to the concrete SQLite implementation. This blocks the WASM build (PR #7 series) where sdk/mpr is unavailable, and prevents testing with mock backends. Introducing a LintReader interface breaks this dependency using Go's implicit interface satisfaction — zero changes needed in the 10+ linter rule files.

Summary

• Define LintReader interface in mdl/linter/context.go with 7 methods matching both *mpr.Reader and MprBackend signatures
• Replace concrete *mpr.Reader dependency with LintReader interface throughout linter and executor packages
• Remove Reader() methods and readerProvider interface from executor — callers now pass Backend() directly
• Zero sdk/mpr imports remain in mdl/linter/ and mdl/executor/ production code

Stacked on

• refactor: quick-win cleanup — panic stubs, SaveToFile, dead code, error handling, syncWriter #4 (pr1-quick-wins)

Test

make build && make test && make lint-go — all pass

[Copilot]

Pull request overview

This PR introduces a linter.LintReader interface to decouple linting/execution code from the concrete sdk/mpr.Reader, routing lint rules through a backend-compatible reader abstraction instead.

Changes:

• Add LintReader to mdl/linter/context.go and thread it through LintContext.
• Update lint rules to consume LintReader instead of *mpr.Reader.
• Remove Executor.Reader() / ExecContext.Reader() and update lint entrypoints to pass Backend() directly.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
mdl/linter/rules/page_navigation_security.go	Switch rule helper to accept linter.LintReader instead of *mpr.Reader.
mdl/linter/context.go	Define LintReader; update LintContext construction and Reader() accessor to use it.
mdl/executor/executor.go	Remove deprecated Reader(); add Backend() accessor for callers.
mdl/executor/exec_context.go	Remove deprecated Reader() from ExecContext.
mdl/executor/cmd_lint.go	Construct LintContext with ctx.Backend directly.
cmd/mxcli/cmd_report.go	Construct LintContext with exec.Backend(); remove Reader() plumbing.
cmd/mxcli/cmd_lint.go	Construct LintContext with exec.Backend(); remove Reader() plumbing.

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[Copilot]

Backend() is documented as returning nil when not connected, but it currently returns e.backend even if IsConnected() is false. This can happen after a failed CONNECT where the previous backend was disconnected but ctx.Backend was never cleared, leaving a non-nil, disconnected backend reachable via Backend(). Either update the implementation to return nil unless e.backend != nil && e.backend.IsConnected(), or adjust the doc comment to reflect the actual behavior.

Suggested change

	func (e *Executor) Backend() backend.FullBackend {
	func (e *Executor) Backend() backend.FullBackend {
	if e.backend == nil || !e.backend.IsConnected() {
	return nil
	}

[Copilot]

Removing Executor.Reader() breaks -tags integration tests that still call it (e.g. mdl/executor/roundtrip_helpers_test.go and roundtrip_doctype_test.go call env.executor.Reader().ProjectVersion()). Update those call sites to use env.executor.Backend().ProjectVersion() (or similar) so make test-integration continues to compile/run.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

---

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[Copilot]

Removing Executor.Reader() breaks any remaining call sites (notably the integration tests under mdl/executor with the integration build tag) that still call env.executor.Reader().ProjectVersion() / similar. Please update those callers to use Executor.Backend().ProjectVersion() (or, if a test truly needs the underlying SDK reader, type-assert on the backend for an MprReader() accessor) so make test-integration continues to compile and run.

Suggested change

	// Reader returns the backend for backward compatibility with older callers.
	// Prefer Backend() in new code.
	func (e *Executor) Reader() backend.FullBackend {
	return e.Backend()
	}