Ring _ Sequence, so that R_(1..3) returns those generators

Nobody has claimed this yet.

This issue was triaged from [`bugs/dan/1-Ring_Sequence`](https://github.com/Macaulay2/M2/blob/388c1ff0ce30d83751dea7bc7eac77fdc1305dd7/bugs/dan/1-Ring_Sequence), one of the 857 files removed from the pre-GitHub `bugs/` tree by [`d2c8d27826`](https://github.com/Macaulay2/M2/commit/d2c8d27826) and catalogued in [#36](https://github.com/Macaulay2/M2/issues/36). **The commentary below was written by Claude (Claude Opus 5, via Claude Code)**, not by @d-torrance, whose account posted it -- please weigh it accordingly.

### The original file, verbatim

```text
David likes this idea:

i12 : Ring _ Sequence := (R,s) -> apply(s,i->R_i);

i14 : R = QQ[a,b,c,d];

i15 : R_(1..3)

o15 = (b, c, d)

o15 : Sequence
```

### Where it stands today

Not installed: `R_(1..3)` still errors with "no method for binary operator `_`" on
`(PolynomialRing, Sequence)`.

### This is convenience rather than a missing capability

Two spellings already do the job, one of them literally the file's own body:

```m2
i1 : R = QQ[a,b,c,d];
i2 : (R_*)_{1,2,3}
o2 = {b, c, d}
i3 : apply(1..3, i -> R_i)
o3 = (b, c, d)
```

`R_*` postdates the file and covers most of what David liked about the idea.

### One detail for whoever takes it

The adjacent slot is occupied, and differently: `R_{1,2,3}` means the **monomial with that exponent
vector**, `a*b^2*c^3`. So `Ring _ List` is not available, while `Ring _ Sequence` is free — which is
convenient, but means the two bracket spellings would mean quite different things, and that asymmetry
should be documented if this goes in.

**#3515** is a different notation request (partial application of functions), not this.

_{`open` · disposition `issue` · source of truth: [`bug-triage/catalog.tsv`](https://github.com/d-torrance/M2/blob/bug-triage/bug-triage/catalog.tsv)}

Start with the Ring _ Sequence example and the current Ring subscript/operator dispatch; the issue does not name an implementation or test file. Compare the existing R_* and R_{1,2,3} behavior, then document or implement the requested distinction so R_(1..3) returns a Sequence of generators without changing monomial notation.

Written by the indexing model from the issue text.