Fix magmap rank bug, magbin typo, plot.magbin speed; add tests and vignette sections

[Copilot]

Thorough audit of the package: two silent bugs, several doc/typo issues, a dead-code remnant, a speed improvement in the hot drawing loop, and materially expanded test and vignette coverage.

Bugs fixed

magmap type='rank' produced no ranking (R/magmap.R)
data[good][order(data[good])] = locut:hicut creates an R temporary copy on the LHS — data was never modified, so every point mapped identically. Replaced with vectorised rank(..., ties.method='average').

# Before: all mapped values were identical (rank never applied)
magmap(c(3,1,4,1,5), type='rank')$map  # → same value repeated

# After: correctly spread across range
magmap(c(3,1,4,1,5), type='rank')$map  # → c(0.27, 0.00, 0.53, 0.00, 0.67) approx

magbin distance deduplication was a no-op (R/magbin.R line 226)
output$output$nn.dists — output$output is NULL, so the assignment silently did nothing. Fixed to output$nn.dists.

Speed: plot.magbin

The per-bin loop checked x$shape on every iteration (constant across all bins) and tested !is.na(colmap$map[i]) in a conditional rather than pre-filtering. Refactored to select the drawing function once outside the loop and iterate only over which(!is.na(colmap$map)). Removed the now-redundant inner count > dustlim guard (bins are already filtered before the loop).

Dead code removed

magband.R: unused .Last.magroj local object (a stale copy of .Last.magproj) removed.

Documentation fixes

File	Fix
man/magclip.Rd	Typos: autoamtic, sepcific, cliped, Locial, "returns" → "returned"
man/magrun.Rd	Return-value names bincen/binlim → bincens/binlims (match code)
man/magmap.Rd	"sue the output" → "use the output"

Tests added (tests/testthat/test-functions.R)

~50 new tests covering previously untested functions: magclip, maghist, magrun (including the corrected return names), magerr, magcurve, magcon, magbar, magcutout, and a regression test for the magmap rank bug.

Vignette additions

New worked-example sections in vignettes/magicaxis.Rmd: magclip, magrun, magerr, magcurve, magbar.