status: add the M53 row — Go carries its first app (Closes #1244)

[drawmeanelephant]

Umbrella #1244 — the one artifact it reserved for the maintainer, plus the closing line.

Closes #1244

What this is

One row in one file: the M53 milestone row in docs/status.md.

+| 54 | Go carries its first app | A Go EL0 program owns a raw ADR 0007 window (`GOWIN.ELF`, gate `go-win`), an independent Go `.tabs` v2 codec round-trips the TABWM session format (`tools/go/tabcodec`), and `WEB.ELF` renders in-guest over `user/go/webrender`; kernel untouched (umbrella #1244) | ✅ 2026-09-15 |

All three sub-cards are already merged — #1245 via #1282 (fafe111), #1246 via #1283 (7b5c204), #1248 via #1258 — so this PR carries the last thing the umbrella names and closes it on merge, which is how this repo closes umbrellas (#1237 by #1243, #1120 by #1147, #934 by #942).

The umbrella's rules forbid cards from declaring docs/status.md ("the maintainer adds the one M53 row at landing"), which is why no card touched it and why this lands as a plain, non-claim PR.

Numbering — worth a look before merging

The table already numbers row 53 as TLS 1.3 client + trust store (landed 2026-09-14), while this arc's own issues call themselves M53 (#1244, #1245, #1246 — and nothing in the TLS13 series uses an M5x label at all). Rows 47–52 all match their umbrella labels (#1237 = M52).

I numbered this row 54 so no two rows share a number and left the TLS row untouched — a one-character edit in review if you'd rather this be 53. The row text is the part that matters; the number is yours to settle.

Verification on the merged baseline (main = 7b5c204, clean tree)

just gates go-                    ->  FLEET RESULT: 6/6 PASS
                                      go-args 13s · go-goroutines 12s · go-hello 17s
                                      go-panic 13s · go-stress 23s · go-win 12s
just go-toolchain                 ->  six fixtures staged, incl. GOWIN.ELF
cd tools/go/tabcodec && go test ./...  ->  ok (10 functions / 25 subtests); gofmt/vet clean
tools/inventory-gates.sh --check  ->  OK
verify-issue-coordination.sh      ->  ok — no file overlaps

artifacts/go-win-report.txt from that run names revision: 7b5c204… branch=main dirty-files=0.

Scope and rollback

Docs only: one inserted line, no code, no gate, no kernel, no persisted state. Revert the single commit to undo. This PR deliberately does not touch the "Open work" row in the same file, which still says the TABWM/DOC follow-ups are "parked until the Go fleet can carry the test apps" — now satisfied, but it is your prose to update, not mine to quietly rewrite.