Add mlr rank verb (#2178)

* stats1: add rank accumulator (#383)

Adds `mlr stats1 -a rank` for standard competition ranking (1,2,2,4,...)
on pre-sorted data, most useful with -s for a rank on every record.

* stats1: make rank order-independent by default, add --rank-sorted opt-in fast path

The rank accumulator previously only compared each value to the immediately
preceding record, silently giving wrong ranks for non-adjacent duplicates
(e.g. unsorted input, or interleaved -g groups). Default to correctly
computing standard competition rank from all values seen so far
(order-independent, buffers values, same approach as percentile
accumulators). Add --rank-sorted for callers who can promise sorted input
and want the previous O(1)-space streaming behavior instead.

* Revert "stats1: make rank order-independent by default, add --rank-sorted opt-in fast path"

This reverts commit aa45a591fe.

* Revert "stats1: add rank accumulator (#383)"

This reverts commit 96deed048a.

* Add mlr rank verb (#383)

Reverts the earlier stats1 -a rank / --rank-sorted approach: stats1 is a
reduce verb (many records -> one summary record per group) and rank is a
per-record annotator, so it never fit cleanly there -- it needed stats1's
-s iterative-stats escape hatch just to be useful, plus a bolted-on
sorted/unsorted split.

mlr rank is a dedicated verb modeled on mlr fraction: -f fields to rank,
-g optional group-by, output field <f>_rank. By default it's a two-pass
algorithm (buffers input, like fraction does) giving standard competition
rank (1,2,2,4,...) that's correct regardless of input order. --sorted
opts into a single-pass, O(1)-space streaming alternative for callers who
can promise pre-sorted input (e.g. via 'mlr sort' first).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* Regenerate docs/man pages after merging main (sparkline verb)

---------

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

man/manpage.txt

@@ -207,11 +207,11 @@
        count-similar cut decimate describe fill-down fill-empty filter flatten
        format-values fraction gap grep group-by group-like gsub having-fields head
        histogram json-parse json-stringify join label latin1-to-utf8 least-frequent
-       merge-fields most-frequent nest nothing put regularize remove-empty-columns
-       rename reorder repeat reshape sample sec2gmtdate sec2gmt seqgen shuffle
-       skip-trivial-records sort sort-within-records sparkline sparsify split ssub
-       stats1 stats2 step sub summary surv tac tail tee template top utf8-to-latin1
-       unflatten uniq unspace unsparsify
+       merge-fields most-frequent nest nothing put rank regularize
+       remove-empty-columns rename reorder repeat reshape sample sec2gmtdate sec2gmt
+       seqgen shuffle skip-trivial-records sort sort-within-records sparkline
+       sparsify split ssub stats1 stats2 step sub summary surv tac tail tee template
+       top utf8-to-latin1 unflatten uniq unspace unsparsify
 
 1mFUNCTION LIST0m
        abs acos acosh antimode any append apply arrayify asin asinh asserting_absent
@@ -1791,6 +1791,34 @@
 
        See also https://miller.readthedocs.io/reference-dsl for more context.
 
+   1mrank0m
+       Usage: mlr rank [options]
+       For each record's value in specified fields, computes the standard
+       competition rank (1,2,2,4,...) of that value among all input records,
+       optionally within groups.
+       E.g. with input records x=10, x=20, x=20, and x=30, emits output records
+       x=10,x_rank=1  x=20,x_rank=2  x=20,x_rank=2  and  x=30,x_rank=4.
+
+       Note: by default this is a two-pass algorithm: on the first pass it retains
+       input records and their values; on the second pass it computes ranks and
+       emits output records, in original input order. This means it produces no
+       output until all input is read, but gives correct ranks regardless of input
+       order. Use --sorted for a single-pass streaming alternative.
+
+       Options:
+       -f {a,b,c} Field name(s) to rank.
+       -g {d,e,f} Optional group-by-field name(s).
+       --sorted   Promise that the input is already sorted by the field(s) being ranked
+                  (within each group, if -g is given). This computes rank in a single
+                  streaming pass and O(1) space, by comparing each record's value only
+                  to the immediately preceding one, rather than buffering all records
+                  to compute an order-independent rank. Produces wrong output if the
+                  input is not in fact sorted.
+       -h|--help  Show this message.
+       Example: mlr rank -f x data/rank-example.csv
+       Example: mlr rank -f x -g g data/rank-example.csv
+       Example: mlr sort -f x then rank -f x --sorted data/rank-example.csv
+
    1mregularize0m
        Usage: mlr regularize [options]
        Outputs records sorted lexically ascending by keys.

man/mlr.1

@@ -249,11 +249,11 @@ altkv bar bootstrap case cat check clean-whitespace count-distinct count
 count-similar cut decimate describe fill-down fill-empty filter flatten
 format-values fraction gap grep group-by group-like gsub having-fields head
 histogram json-parse json-stringify join label latin1-to-utf8 least-frequent
-merge-fields most-frequent nest nothing put regularize remove-empty-columns
-rename reorder repeat reshape sample sec2gmtdate sec2gmt seqgen shuffle
-skip-trivial-records sort sort-within-records sparkline sparsify split ssub
-stats1 stats2 step sub summary surv tac tail tee template top utf8-to-latin1
-unflatten uniq unspace unsparsify
+merge-fields most-frequent nest nothing put rank regularize
+remove-empty-columns rename reorder repeat reshape sample sec2gmtdate sec2gmt
+seqgen shuffle skip-trivial-records sort sort-within-records sparkline
+sparsify split ssub stats1 stats2 step sub summary surv tac tail tee template
+top utf8-to-latin1 unflatten uniq unspace unsparsify
 .fi
 .if n \{\
 .RE
@@ -2209,6 +2209,40 @@ See also https://miller.readthedocs.io/reference-dsl for more context.
 .fi
 .if n \{\
 .RE
+.SS "rank"
+.if n \{\
+.RS 0
+.\}
+.nf
+Usage: mlr rank [options]
+For each record's value in specified fields, computes the standard
+competition rank (1,2,2,4,...) of that value among all input records,
+optionally within groups.
+E.g. with input records x=10, x=20, x=20, and x=30, emits output records
+x=10,x_rank=1  x=20,x_rank=2  x=20,x_rank=2  and  x=30,x_rank=4.
+
+Note: by default this is a two-pass algorithm: on the first pass it retains
+input records and their values; on the second pass it computes ranks and
+emits output records, in original input order. This means it produces no
+output until all input is read, but gives correct ranks regardless of input
+order. Use --sorted for a single-pass streaming alternative.
+
+Options:
+-f {a,b,c} Field name(s) to rank.
+-g {d,e,f} Optional group-by-field name(s).
+--sorted   Promise that the input is already sorted by the field(s) being ranked
+           (within each group, if -g is given). This computes rank in a single
+           streaming pass and O(1) space, by comparing each record's value only
+           to the immediately preceding one, rather than buffering all records
+           to compute an order-independent rank. Produces wrong output if the
+           input is not in fact sorted.
+-h|--help  Show this message.
+Example: mlr rank -f x data/rank-example.csv
+Example: mlr rank -f x -g g data/rank-example.csv
+Example: mlr sort -f x then rank -f x --sorted data/rank-example.csv
+.fi
+.if n \{\
+.RE
 .SS "regularize"
 .if n \{\
 .RS 0