Fix BUG-011: wrap fanned plan-DAG group members onto multiple lines

[anutron]

What

When a large group is fanned out in the plan-DAG view, its member boxes rendered in a single horizontal row that overflowed the pane (only a › hinted at the rest). Now they wrap onto multiple rows to fit the width.

Fix

internal/tui/planview packs fanned-group member boxes per row until the pane width is exceeded, then starts a new row; cursor nav reflows across the wrapped grid and the downstream/feed edge re-anchors under the taller block. Reuses the dagview box widths (rune-width-aware); no relayout/shrink. Coexists with #795's cancelled/failed-state rendering (resolved on rebase keeping both).

Tests / spec

• +156 lines of render tests: a many-member group wraps onto N rows (none overflow), the cursor reaches every member, the downstream edge still draws — at narrow widths.
• golangci-lint v2.11.4 --new-from-rev → 0 issues; go test ./internal/tui/planview/ ./internal/tui/ green; build + gofmt clean.
• OpenSpec change fix-bug-011-fan-wrap (hera-view delta, validates --strict); gotcha bullet added.

Rebased onto current master (incl. #795); feature-only diff.

🤖 Generated with Claude Code

[github-actions]

Merging this branch will decrease overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/drn/argus/internal/tui/planview	93.70% (-0.01%)	👎

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/drn/argus/internal/tui/planview/planview.go	93.70% (-0.01%)	937 (+30)	878 (+28)	59 (+2)	👎

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/drn/argus/internal/tui/planview/render_test.go