Fix numerical instability in tick generation (division by zero / NaN propagation)

[samanthataylor3]

Closes #3

Describe your changes:

Two defects in src/plugins/plot/tickUtils.js allow non-finite values (Infinity, NaN) to propagate into plot rendering, corrupting tick marks or causing infinite loops.

Defect 1 — tickStep() / timeTickStep() division by zero:

Math.abs(stop - start) / Math.max(0, count)
//                                ^ allows count=0 → Infinity

Changed Math.max(0, count) → Math.max(1, count) in both functions to guarantee a positive divisor.

Defect 2 — getLogTicks() passes non-positive count to ticks():

ticks(..., secondaryTickCount - 2)
// when secondaryTickCount ≤ 2  →  count ≤ 0  →  triggers Defect 1

This is hit in practice: MctTicks.vue calls getLogTicks(…, SECONDARY_TICK_NUMBER) where SECONDARY_TICK_NUMBER = 2, so secondaryTickCount - 2 = 0.

Clamped to Math.max(1, secondaryTickCount - 2) and added an early-return guard in ticks() itself for defense-in-depth.

All 4 locations fixed in one file:

Location	Fix
tickStep() L23	Math.max(0, count) → Math.max(1, count)
timeTickStep() L41	same
getLogTicks() L223	secondaryTickCount - 2 → Math.max(1, secondaryTickCount - 2)
ticks() L237	early return [] when count < 1

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Link to Devin session: https://app.devin.ai/sessions/dcf6ca69fe8f4bd88047d072b3daeb19
Requested by: @samanthataylor3

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Original prompt from Samantha

Can you look at the issues in @COG-GTM/openmct, choose the ticket that is most straightforward to implement, and make the changes and create a PR?

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