Polish Lite chart axes and sub-tab styling

[erikdarlingdata]

Summary

Small set of Lite UI polish items reviewed in-session:

• Chart X-axis date ticks — the date line now prints only on the first tick and on ticks where the date changes; all other ticks show time only. Format respects the current culture (en-GB shows dd/MM, de-DE shows dd.MM, 24-hour clocks, etc.). Implemented as a DateTimeTicksBottomDateChange() extension in Lite/Helpers/AxesExtensions.cs and applied at every DateTimeTicksBottom() call site in ServerTab and CorrelatedTimelineLanesControl.
• Server name deduped in header — ConnectionStatusText no longer prefixes the server name before Last refresh: … since ServerNameText already shows it. Initial value is Connecting... instead of the server name.
• Chart tick font size bumped from 12 → 13 for readability, applied in both ApplyTheme and ReapplyAxisColors so it survives DateTimeTicksBottom resets.
• SubTabItemStyle added to all three themes (Dark / Light / CoolBreeze) and wired up on the six sub-TabControls in ServerTab.xaml (Queries, Memory, File I/O, Blocking, plus two unnamed). Sub-tabs now use a thin accent underline with transparent background instead of the filled-cyan block, so sub-tab selection no longer looks identical to main-tab selection.

Test plan

• Launch Lite in Dark / Light / CoolBreeze themes; verify sub-tabs render with accent underline, main tabs still filled
• Connect to any server; watch the header — Connecting... → Last refresh: HH:mm:ss (…) with no duplicate server name
• View any trend chart that spans < 24 hours — date shows once on first tick, time-only on the rest
• View any trend chart spanning a midnight boundary — date appears again at the rollover tick
• Switch Windows display language (or use CultureInfo locally) to en-GB / de-DE and verify date format and 24-hour times
• Verify Overview tab's File I/O lane (the only lane with visible bottom ticks) also follows the new formatter

🤖 Generated with Claude Code

[erikdarlingdata]

Review summary

What this does
Lite UI polish: (1) new DateTimeTicksBottomDateChange() extension replaces DateTimeTicksBottom() at every call site in ServerTab.xaml.cs and CorrelatedTimelineLanesControl.xaml.cs, printing the date only when it changes; (2) ConnectionStatusText stops duplicating the server name already shown in ServerNameText; (3) chart tick font bumped 12 → 13 in both ApplyTheme and ReapplyAxisColors; (4) new SubTabItemStyle added to Dark/Light/CoolBreeze themes and applied to the six sub-TabControls in ServerTab.xaml.

Process checks

• Base branch is dev ✓
• Lite-only — no Dashboard port needed, and Lite-first is the correct ordering ✓
• No PlanAnalyzer.cs changes — sync check N/A
• No SQL / install / upgrade changes — schema-path check N/A
• No .github/workflows/build.yml changes — SignPath check N/A

Needs attention (details inline)

1. Lite/Helpers/AxesExtensions.cs:31-42 — the lastDate closure persists across ScottPlot render passes, so after a zoom/pan the first visible tick of the new view may not show the date. This is the main correctness issue.
2. Lite/Controls/ServerTab.xaml.cs:844 — header time string is still hardcoded HH:mm:ss while the chart-tick formatter this PR adds is culture-aware; minor inconsistency.
3. Lite/Themes/{Dark,Light,CoolBreeze}Theme.xaml SubTabItemStyle — custom ControlTemplate has no keyboard-focus visual; minor a11y nit.

Other notes

• BuildMonthDayPattern() at AxesExtensions.cs:12-19 — the regex-based stripping of the year component will produce unexpected output for cultures whose ShortDatePattern has the year in the middle (rare, but e.g. some locale customisations). The fallback to "M/d" only triggers if the result is whitespace, not if it's malformed. Low risk but worth a glance.
• Test plan in the PR description is appropriate for UI polish; no unit tests warranted.

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Generated by Claude Code

[erikdarlingdata]

Correctness concern: lastDate is captured in a closure and persists across ScottPlot render passes after the formatter is installed. The state is only reset when DateTimeTicksBottomDateChange() is called again (new closure), which happens on full chart refresh — but not on zoom/pan, where ScottPlot re-invokes the existing LabelFormatter for new visible ticks.

Concrete failure mode: chart shows Apr 15 → Apr 18. Last rendered tick is Apr 18, so lastDate ends at Apr 18. User zooms into a 1-hour window within Apr 18. All visible ticks have dt.Date == lastDate.Value, so the formatter returns time-only for every one of them — the date line never appears in the zoomed view, even though the contract is "first tick gets the date."

There's also an ordering assumption: the state machine only works if ScottPlot iterates ticks in chronological order. If it ever calls the formatter out of order (or twice for the same tick during layout), the output will flicker.

Safer approach: compute the "show date?" decision from the tick positions array after ticks are generated, rather than via stateful closure. ScottPlot's DateTimeAutomatic exposes Ticks after regeneration — you can iterate once and assign labels via a precomputed dictionary, or hook the regeneration event if one is available.

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Generated by Claude Code

[erikdarlingdata]

Minor inconsistency: the chart-tick formatter this PR introduces is culture-aware (uses "t" and culture-specific month-day pattern), but this status line is still hardcoded HH:mm:ss. For an en-US user the chart shows 3:45 PM while the header shows 15:45:03. Either pick one policy or use DateTime.Now.ToString("T", CultureInfo.CurrentCulture) for consistency.

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Generated by Claude Code

[erikdarlingdata]

The custom ControlTemplate replaces the default TabItem template without setting a FocusVisualStyle or any visual cue for IsKeyboardFocused/IsFocused. Users navigating by keyboard won't see which sub-tab is focused when tabbing through the UI. Consider adding a FocusVisualStyle setter or a trigger on IsKeyboardFocused that changes the border/background. Same applies to the identical style in LightTheme.xaml and CoolBreezeTheme.xaml.

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Generated by Claude Code