Handoff — 2026-08-31 — project tree window

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# Handoff — 2026-08-31 — project tree window

## State

**Ticket 0003 is done and green**, on branch `feature/treeview-window`, **uncommitted**.

`F9`, or **Window ▸ Project tree**, opens a window listing the project's files. Arrows walk it, `→`/`←` open and close branches, `Enter` opens a file, `F5`/`Ctrl-R` re-reads.

```
╔═[x]════════════ turbo-go ════════════2═[■]╗
║ ▶ .turbo-go                              ║
║ ▼ internal                               ║
║   ▶ app                                  ║
║   go.mod                                 ║
╚══════════════════════════════════════════╝
```

- New `internal/filetree` (94.7 %, 41 tests), 10 more in `internal/app`.
- Four `tree.*` theme keys, set in all three shipped themes and enforced by the existing completeness test.
- Whole suite green under `-race`. Quality gate **PASS** first time: 0/0/0, complexity 1228.
- Docs complete in EN and FR — three new pages each, six existing pages updated each. `docs/diagrams/packages.drawio` gained `filetree`; re-checked against `go list`, 31 edges each side.
- **Verified by rendering the real binary through the project's own VT emulator**: `F9` lists with `.git` hidden, `→` nests two levels, `Enter` opens a file into a third window.

Earlier the same day, PR #3 merged the window frame boxes and the Open-dialog OK fix.

## In flight

Nothing. Finished through Phase 8.

## Next steps

1. **Commit and open the PR.** `feature/treeview-window` is the branch.
2. **Drive the tree with a real mouse.** Everything went through code and the emulator; clicking a row, the second-click-to-open rule and the wheel have never been exercised by hand.
3. **Tickets.** 0002, 0003 and 0007 are all implemented and all still `state: open`.

## Open questions / blockers

- **`.gitignore` is not respected.** The tree shows `bin/`, `release/` and anything else git ignores. Hiding them would be genuinely nicer and costs a gitignore pattern engine — negation, `**`, anchoring — which is a feature to decide on rather than a detail to slip in. Recorded in the explanation page as turned down *for now*.
- **The root is the working directory, not the module root.** Start the editor from `internal/app` and the tree shows only that. This was the user's choice, for one rule across the whole editor; if it turns out to annoy in practice, `main.moduleRoot` is already there and already tested.
- **A docked side panel was turned down**, not rejected forever. If it is wanted, it is a `ui` feature — `Desktop` needs reserved edges that `fitInto`, the grow modes, maximise, tile and cascade all respect — and should be designed on its own terms rather than arriving with a file browser.

## Watch out for

- **The tree's theme keys are not decoration.** `list.selected` is coloured against a *dialog*: turbo-classic makes it white on navy, and `window.body` is navy. Borrowing it would make the selected row invisible in the editor's default theme. `TestTheHighlightIsVisibleInEveryShippedTheme` fails at 0 channel values if anyone "simplifies" `tree.selected` back to the list colours — I checked by doing exactly that.
- **`testDirectory` in `internal/app` does not create intermediate directories.** `testDirectory(t, "internal/app.go")` fails; use `"internal/"` and a separate file. `makeTree` in `internal/filetree` *does* nest, which is easy to confuse when moving a fixture between the two packages.
- **Refresh must not walk the project.** `Node.refresh` returns immediately for a directory that was never loaded, and `TestRefreshLeavesUnopenedDirectoriesUnread` is what stops that being lost. Removing the guard would turn every save into a full-tree walk.
- **`left` on a row has two meanings and both matter.** On an open directory it collapses; on anything else it moves to the parent — found as the nearest row above with a smaller depth, which needs no parent pointer. Making it only collapse turns it into a no-op on every file, which is most rows.
- **Collapsing can leave the highlight past the last row.** `keepSelectionInRange` after every toggle is what prevents it; `TestCollapsingABranchKeepsTheHighlightOnARow` covers it.
- **`a.treeWindow` must be cleared when the window closes**, or `F9` tries to focus a window that is no longer on the desktop. `closeWindow` has a branch for it beside the terminal one.