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>

docs/RELEASE-0.10-TASKS.md

@@ -109,13 +109,13 @@ Done first because both share a compact, single-line record formatter.
 - [x] T4.4 — persistence + restored-paused tests
 
 ### Phase 5 — Window sizing
-- [ ] T5.1 — 720p-safe default + MinSize
+- [x] T5.1 — 720p-safe default + MinSize
 
 ### Phase 6 — Refactor + cleanup
-- [ ] T6.1 — `jobs_view.go` split
-- [ ] T6.2 — post-field-test cleanup (keep startup timing)
-- [ ] T6.3 — drop YAML→JSON migration
-- [ ] T6.4 — ARCHITECTURE.md update
+- [x] T6.1 — `jobs_view.go` split
+- [x] T6.2 — post-field-test cleanup (keep startup timing)
+- [x] T6.3 — drop YAML→JSON migration
+- [x] T6.4 — ARCHITECTURE.md update
 
 ### Phase 7 — Portable packaging
 - [ ] T7.1 — Windows `.zip`