01. Rearchitect nav model — remove the sidebar pane

meta: id: yazi-remake-01 feature: yazi-remake priority: P1 depends_on: [] tags: [implementation, nav-model, tests-required]

objective:

Remove the always-on SIDEBAR_PANE concept from the navigation context so activeTab is plain tab state (not a pane), establishing clean parent|current|preview semantics for the yazi remake.

deliverables:

src/context/NavigationContext.tsx — delete SIDEBAR_PANE constant and all references; activeTab is no longer a pane
src/utils/navigation.ts — update TabPaneCount semantics; depth-tabs = 1 focusable pane (current), the 3 visible columns are a render concern not 3 panes
Updated header/comment block describing the parent|current|preview model
swipe() / popDepth() reworked: depth-tabs l=drill (open), h=pop (noop at depth 0); fixed-pane tabs h/l move between parent/current/preview
Tab-enter resets focus to DEPTH_CENTER_PANE (current pane), not a sidebar

steps:

Audit every reference to SIDEBAR_PANE across the codebase (grep)
In NavigationContext.tsx: delete the SIDEBAR_PANE = -1 export and the focusedIndex/setFocusedIndex SIDEBAR_PANE branch added previously
Set the initial activePane signal and the tab-switch createEffect to reset to DEPTH_CENTER_PANE (the current pane), not SIDEBAR_PANE
Rework swipe() to clamp to [0, paneCount-1] for fixed-pane tabs (the sidebar is no longer in the chain); depth-tabs don't use swipe for drill/pop (that lives in Shell dispatch)
In utils/navigation.ts: confirm TabPaneCount reflects focusable content panes only (depth-tabs = 1, Search = 3, Player = 1); update PANE_RATIO leave-behind note (ratio change happens in task 02)
Update the file header comment block to describe parent|current|preview
Run lens_diagnostics on the two files

tests:

Unit: focusedIndex(DEPTH_CENTER_PANE) on a depth-tab returns the top frame's focus; setFocusedIndex writes to the top frame (Arrange a tab with a 2-frame stack, Act by calling setFocusedIndex, Assert topFrame.focus updated)
Integration: tab-switch effect sets activePane to DEPTH_CENTER_PANE (not -1); swipe(-1, 3) on a fixed tab clamps to 0 not -1
e2e (harness): app boots with nav.state.pane === 0 (current), not -1

acceptance_criteria:

validation:

grep -rn "SIDEBAR_PANE" src/ returns nothing
bun run build passes
lens_diagnostics paths=[src/context/NavigationContext.tsx,src/utils/navigation.ts] severity=error → 0 findings

notes:

This task unblocks 03/04/05/06. It must not delete DEPTH_CENTER_PANE — that constant is generalised to "the current pane" and retained
SIDEBAR_ACTIONS (added in Shell in a prior turn) is removed in task 06 (the keybind rewrite), not here — but Shell will temporarily fail to compile after this task until 05/06 land; that's expected and the build command ignores type errors, so gate success on grep + targeted diagnostics, not the full build