feat(linter): propagate workflow:rules:variables: into job rule evaluation

workflow:rules: can define variables: on matching rules (GitLab CI 15.0+).
These variables are now injected into the evaluation context before job
rules:if: expressions are evaluated, making patterns like:

  workflow:
    rules:
      - if: '$CI_COMMIT_BRANCH == "main"'
        variables:
          DEPLOY_TARGET: production
  deploy:
    rules:
      - if: '$DEPLOY_TARGET == "production"'

work correctly with glint check --branch main.

Changes:
- model.Rule: add Variables map[string]any field (yaml:"variables")
- cicontext.Context: add pinned map tracking which vars must not be
  overwritten; New() pins all shortcut and --var variables; add
  Inject(key, value) which writes only when key is not pinned
- cicontext.ExtractStringVars: shared helper that converts map[string]any
  variable blocks (plain string or {value:...} form) to map[string]string
- cicontext.EvalWorkflow: returns (bool, map[string]string) — the vars of
  the matching workflow rule alongside the runs/no-runs result
- cmd/glint/main.go: enrichContext() injects pipeline-level variable
  defaults then workflow-rule variables before printContext; applied in
  both cmdCheck and cmdGraph

Injection priority (highest wins):
  --var CLI overrides > --branch/--tag/--source shortcuts
  > workflow-rule variables > pipeline variables: defaults

Adds 15 unit tests (TestEvalWorkflow, TestContextInject,
TestExtractStringVars, TestWorkflowVarsJobEval) and a testdata fixture
(workflow_vars.yml) validated across four branch contexts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/cicontext/reachability_test.go

@@ -0,0 +1,243 @@
+package cicontext
+
+import (
+	"testing"
+
+	"git.k3nny.fr/glint/internal/model"
+)
+
+func TestEvalWorkflow(t *testing.T) {
+	makePipeline := func(rules []model.Rule) *model.Pipeline {
+		return &model.Pipeline{Workflow: &model.Workflow{Rules: rules}}
+	}
+
+	tests := []struct {
+		name     string
+		rules    []model.Rule
+		branch   string
+		wantRuns bool
+		wantVars map[string]string
+	}{
+		{
+			name:     "no workflow block",
+			rules:    nil,
+			branch:   "main",
+			wantRuns: true,
+			wantVars: nil,
+		},
+		{
+			name: "matching rule runs always",
+			rules: []model.Rule{
+				{If: `$CI_COMMIT_BRANCH == "main"`, When: "always"},
+			},
+			branch:   "main",
+			wantRuns: true,
+		},
+		{
+			name: "matching rule when never",
+			rules: []model.Rule{
+				{If: `$CI_COMMIT_BRANCH == "main"`, When: "never"},
+			},
+			branch:   "main",
+			wantRuns: false,
+		},
+		{
+			name: "no rule matched",
+			rules: []model.Rule{
+				{If: `$CI_COMMIT_BRANCH == "main"`},
+			},
+			branch:   "develop",
+			wantRuns: false,
+		},
+		{
+			name: "matching rule with variables",
+			rules: []model.Rule{
+				{
+					If:   `$CI_COMMIT_BRANCH == "main"`,
+					When: "always",
+					Variables: map[string]any{
+						"DEPLOY_TARGET": "production",
+						"ENVIRONMENT":   "prod",
+					},
+				},
+				{When: "always"},
+			},
+			branch:   "main",
+			wantRuns: true,
+			wantVars: map[string]string{
+				"DEPLOY_TARGET": "production",
+				"ENVIRONMENT":   "prod",
+			},
+		},
+		{
+			name: "fallback rule with different variables",
+			rules: []model.Rule{
+				{If: `$CI_COMMIT_BRANCH == "main"`, Variables: map[string]any{"DEPLOY_TARGET": "production"}},
+				{When: "always", Variables: map[string]any{"DEPLOY_TARGET": "staging"}},
+			},
+			branch:   "develop",
+			wantRuns: true,
+			wantVars: map[string]string{"DEPLOY_TARGET": "staging"},
+		},
+		{
+			name: "empty context always runs",
+			rules: []model.Rule{
+				{If: `$CI_COMMIT_BRANCH == "main"`, When: "never"},
+			},
+			branch:   "", // no context
+			wantRuns: true,
+			wantVars: nil,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			var p *model.Pipeline
+			if tc.rules == nil {
+				p = &model.Pipeline{}
+			} else {
+				p = makePipeline(tc.rules)
+			}
+			ctx := New(tc.branch, "", "", nil)
+			runs, vars := EvalWorkflow(p, ctx)
+			if runs != tc.wantRuns {
+				t.Errorf("EvalWorkflow runs = %v, want %v", runs, tc.wantRuns)
+			}
+			for k, want := range tc.wantVars {
+				if got := vars[k]; got != want {
+					t.Errorf("EvalWorkflow vars[%q] = %q, want %q", k, got, want)
+				}
+			}
+			if len(vars) != len(tc.wantVars) {
+				t.Errorf("EvalWorkflow returned %d vars, want %d; got %v", len(vars), len(tc.wantVars), vars)
+			}
+		})
+	}
+}
+
+func TestContextInject(t *testing.T) {
+	t.Run("inject does not overwrite pinned var", func(t *testing.T) {
+		ctx := New("main", "", "", []string{"DEPLOY_TARGET=override"})
+		ctx.Inject("DEPLOY_TARGET", "workflow-value")
+		if got := ctx.Get("DEPLOY_TARGET"); got != "override" {
+			t.Errorf("Inject overwrote pinned var: got %q, want %q", got, "override")
+		}
+	})
+	t.Run("inject does not overwrite shortcut var", func(t *testing.T) {
+		ctx := New("main", "", "", nil)
+		ctx.Inject("CI_COMMIT_BRANCH", "other")
+		if got := ctx.Get("CI_COMMIT_BRANCH"); got != "main" {
+			t.Errorf("Inject overwrote shortcut var: got %q, want %q", got, "main")
+		}
+	})
+	t.Run("inject sets new variable", func(t *testing.T) {
+		ctx := New("main", "", "", nil)
+		ctx.Inject("DEPLOY_TARGET", "production")
+		if got := ctx.Get("DEPLOY_TARGET"); got != "production" {
+			t.Errorf("Inject did not set variable: got %q", got)
+		}
+	})
+	t.Run("inject later call overrides earlier call", func(t *testing.T) {
+		ctx := New("main", "", "", nil)
+		ctx.Inject("DEPLOY_TARGET", "pipeline-default")
+		ctx.Inject("DEPLOY_TARGET", "workflow-override")
+		if got := ctx.Get("DEPLOY_TARGET"); got != "workflow-override" {
+			t.Errorf("second Inject did not win: got %q, want %q", got, "workflow-override")
+		}
+	})
+}
+
+func TestExtractStringVars(t *testing.T) {
+	tests := []struct {
+		name string
+		in   map[string]any
+		want map[string]string
+	}{
+		{
+			name: "plain strings",
+			in:   map[string]any{"A": "hello", "B": "world"},
+			want: map[string]string{"A": "hello", "B": "world"},
+		},
+		{
+			name: "extended value form",
+			in: map[string]any{
+				"KEY": map[string]any{"value": "extended", "description": "some desc"},
+			},
+			want: map[string]string{"KEY": "extended"},
+		},
+		{
+			name: "mixed forms",
+			in: map[string]any{
+				"PLAIN":   "str",
+				"COMPLEX": map[string]any{"value": "val"},
+			},
+			want: map[string]string{"PLAIN": "str", "COMPLEX": "val"},
+		},
+		{
+			name: "nil map",
+			in:   nil,
+			want: nil,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := ExtractStringVars(tc.in)
+			for k, want := range tc.want {
+				if got[k] != want {
+					t.Errorf("ExtractStringVars[%q] = %q, want %q", k, got[k], want)
+				}
+			}
+			if len(got) != len(tc.want) {
+				t.Errorf("ExtractStringVars returned %d entries, want %d", len(got), len(tc.want))
+			}
+		})
+	}
+}
+
+// TestWorkflowVarsJobEval verifies the end-to-end flow: workflow rule injects
+// DEPLOY_TARGET, which is then used in a job's rules:if: expression.
+func TestWorkflowVarsJobEval(t *testing.T) {
+	rules := []model.Rule{
+		{If: `$CI_COMMIT_BRANCH == "main"`, Variables: map[string]any{"DEPLOY_TARGET": "production"}},
+		{When: "always", Variables: map[string]any{"DEPLOY_TARGET": "staging"}},
+	}
+	p := &model.Pipeline{
+		Workflow: &model.Workflow{Rules: rules},
+		Jobs: map[string]model.Job{
+			"deploy-prod": {
+				Rules: []model.Rule{
+					{If: `$DEPLOY_TARGET == "production"`, When: "on_success"},
+					{When: "never"},
+				},
+			},
+			"deploy-staging": {
+				Rules: []model.Rule{
+					{If: `$DEPLOY_TARGET == "staging"`, When: "on_success"},
+					{When: "never"},
+				},
+			},
+		},
+	}
+
+	for _, tc := range []struct {
+		branch      string
+		wantProd    JobState
+		wantStaging JobState
+	}{
+		{"main", JobActive, JobSkipped},
+		{"develop", JobSkipped, JobActive},
+	} {
+		ctx := New(tc.branch, "", "", nil)
+		_, ruleVars := EvalWorkflow(p, ctx)
+		for k, v := range ruleVars {
+			ctx.Inject(k, v)
+		}
+		if got := EvalJob(p.Jobs["deploy-prod"], ctx); got != tc.wantProd {
+			t.Errorf("branch=%q deploy-prod = %v, want %v", tc.branch, got, tc.wantProd)
+		}
+		if got := EvalJob(p.Jobs["deploy-staging"], ctx); got != tc.wantStaging {
+			t.Errorf("branch=%q deploy-staging = %v, want %v", tc.branch, got, tc.wantStaging)
+		}
+	}
+}