refactor: split jobs_view, drop YAML migration, update docs (T6.1-T6.4)

T6.1: split jobs_view.go into three files — jobs_view_helpers.go (pure
helpers) and jobs_view_details.go (detailsPanel struct with widget
creation, update, clear, and container methods) — bringing jobs_view.go
from 459 to ~200 lines.

T6.2: remove stale YAML upgrade note from README; drop *.yaml from
.dockerignore.

T6.3: delete YAML shadow structs (yamlConfig/yamlJob/yamlJobsFile),
importYAMLConfig/importYAMLJobs, legacy path constants, and all
YAML-import tests; run go mod tidy to remove go.yaml.in/yaml/v4.

T6.4: refresh ARCHITECTURE.md — JSON storage references, new Key Domain
Concepts section (per-job overlap policy, run-time statistics + log
seeding, persisted pause flag, jobs_view split).

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

go.sum

@@ -71,8 +71,6 @@ github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/yuin/goldmark v1.7.8 h1:iERMLn0/QJeHFhxSt3p6PeN9mGnvIKSpG9YYorDMnic=
 github.com/yuin/goldmark v1.7.8/go.mod h1:uzxRWxtg69N339t3louHJ7+O03ezfj6PlliRlaOzY1E=
-go.yaml.in/yaml/v4 v4.0.0-rc.5 h1:JVliQq9EGOYaTgMi+k8BhUJyqcGk4ZqeuiN1Cirba9c=
-go.yaml.in/yaml/v4 v4.0.0-rc.5/go.mod h1:aZqd9kCMsGL7AuUv/m/PvWLdg5sjJsZ4oHDEnfPPfY0=
 golang.org/x/image v0.24.0 h1:AN7zRgVsbvmTfNyqIbbOraYL8mSwcKncEj8ofjgzcMQ=
 golang.org/x/image v0.24.0/go.mod h1:4b/ITuLfqYq1hqZcjofwctIhi7sZh2WaCjvsBNjjya8=
 golang.org/x/net v0.35.0 h1:T5GQRQb2y08kTAByq9L4/bz8cipCdA8FbRTXewonqY8=