refactor: extract the Jobs view state, track selection by job ID

Phase 10 of the whole-project review (findings 5.1 and 5.2), folded into
the ROADMAP file-split item as that plan asks.

5.2 was a real defect. `selected` was an index into a snapshot of the jobs
slice, and every path that changed the slice patched it by hand. The one
path that could not — adopting a different jobs file, where the Service
replaces the whole list and the view only hears about it through the
refresh JobsLoaded triggers — left the details pane redrawing from an
index that belonged to the previous list, describing whichever job now sat
there (or clearing when the new list was shorter) while the list highlight
stayed put. The selection is now a job ID; rows are derived from it at
render time, and refresh ends by pointing the highlight at the selected
job, so the two can no longer disagree.

5.1: newJobsView was one 330-line constructor whose dozen closures shared
seven mutable locals. It is now a jobsView struct over a jobsViewState
that owns the snapshot, the folder filter, and the selection — the
invariant that used to be maintained by hand in five places lives in one
place — split across jobs_view.go (construction, refresh, layout),
jobs_view_state.go, jobs_view_list.go, and jobs_view_toolbar.go. The
folder-option rebuild that appeared verbatim in three handlers is one
method.

Behaviour that changed beyond the fix: switching the folder filter keeps
the current selection when the new filter still shows it, instead of
always jumping to the folder's first job.

Docs: ARCHITECTURE records the new file layout and the selection-by-ID
contract; ROADMAP drops jobs_view.go from the over-guideline table and
refreshes the other five numbers (finding 2.4); TESTS documents the new
state test file and the adoption regression test.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -123,24 +123,24 @@ Design notes / open questions:
 
 [ARCHITECTURE.md](ARCHITECTURE.md) sets a ~250-line guideline per source file
 and records the `jobs_view.go` and `settings_view.go` splits as the worked
-examples. Six non-test files are over it at 1.0.0, including both files that
-were already split once:
+examples. `jobs_view.go` was split again in 1.0.2 — into view, state, list, and
+toolbar — because the selection defect it carried was a symptom of the size
+(one 330-line constructor over seven shared locals). Five non-test files are
+over the guideline as of that pass:
 
 | File | Lines |
 |------|-------|
-| `src/app/operations.go` | 490 |
-| `src/ui/jobs_view.go` | 355 |
-| `src/app/run.go` | 287 |
-| `src/ui/history_view.go` | 282 |
-| `src/ui/settings_view.go` | 277 |
-| `src/storage/store.go` | 265 |
+| `src/app/operations.go` | 529 |
+| `src/ui/history_view.go` | 373 |
+| `src/storage/store.go` | 365 |
+| `src/ui/settings_view.go` | 318 |
+| `src/app/run.go` | 274 |
 
-This is deliberately deferred to the next whole-project review rather than done
-piecemeal: a future review already asks item 2 to look for exactly this,
-a split touches every reader of the file, and doing all six in one pass keeps
-the seams consistent instead of settling them six different ways. Splitting is
+The remaining five are deliberately deferred rather than done piecemeal: a
+split touches every reader of the file, and doing them in one pass keeps the
+seams consistent instead of settling them five different ways. Splitting is
 also the kind of change that reads as pure movement while quietly dropping a
-function, so it wants one careful pass, not six hurried ones.
+function, so it wants one careful pass, not five hurried ones.
 
 Seams visible today, as a starting point rather than a decision:
 
@@ -152,13 +152,15 @@ Seams visible today, as a starting point rather than a decision:
 - **`history_view.go`** — the column-measuring helpers (`textWidth` through
   `historyColumnWidths`) are pure, already unit-tested, and independent of the
   table they size.
-- **`jobs_view.go`** — nearly all of it is one `newJobsView` constructor, so the
-  split has to break that function up (list template, toolbar handlers,
-  assembly) rather than move whole functions. Larger judgement call than the
-  others.
-- **`run.go`**, **`settings_view.go`**, **`store.go`** — barely over. Worth
-  re-measuring at the time; if a pass elsewhere has shrunk them, leave them
-  alone rather than splitting for the sake of the number.
+- **`store.go`** — path resolution, the config load/normalize path, and the jobs
+  load/normalize path are three separate concerns in one file.
+- **`run.go`**, **`settings_view.go`** — barely over. Worth re-measuring at the
+  time; if a pass elsewhere has shrunk them, leave them alone rather than
+  splitting for the sake of the number.
+
+The `jobs_view.go` pass is the worked example for the rest: the constructor was
+broken up along the state it shared, not along line count, and the split landed
+with the selection fix rather than promising it separately.
 
 Scope note: the guideline is about source files. Test files are much larger and
 that is fine — a table-driven test file grows with the cases it covers.