Proper Extended type support (currently aliased to Double)

SUPERSEDED 2026-08-30 → [[feature-a-extended-is-an-alias-for-double]]. Do not work this ticket. Three overlapping umbrellas existed in three folders (rainy-day/, float/, plus the Track U decide in backlog/); the float/ one carried the only real scope analysis, so it became the umbrella and this file is kept only so the inbound citations below still resolve.

• Type: feature (compiler) — Track A
• Status: superseded (was: rainy-day)
• Opened: 2026-06-22
• Owner: — (Track A / "sis")

Why this file still exists

It is cited from three places that would otherwise dangle:

• float/bug-b-rounding-api-gaps-setroundmode-roundto-lround.md:113 — "targets Single + Double only ([[feature-extended-type-support]])"
• rainy-day/goal-compile-fpc-compiler.md:151
• done/feature-float-math-and-demo.md:13

Renaming or deleting would break those links for a grouping the umbrella already provides, which is the same reasoning meta-float-accuracy-policy gives for not re-slugging the float cluster.

Original goal (kept verbatim)

Real Extended support. Right now Extended is cheated as Double (see feature-extended-alias-or-reject, done). The user does not want to invest in true 80-bit Extended yet; libraries must keep working under the alias.

Constraints / notes (kept verbatim)

• Until this lands, RTL libraries target Single + Double only and assume Extended = Double. lib/rtl/math.pas intentionally provides only Single + Double overloads (no Extended).
• True Extended means an 80-bit x87 path on i386/x86-64 (and a decision for targets without 80-bit hardware — soft-float or reject). Interacts with feature-real-cross-target-consistency.

Log

• 2026-06-22 — Filed by Track B while building the math library; deferred per user (Extended not a priority until properly supported).
• 2026-08-30 — Superseded. Owner ruled Extended will be implemented properly eventually, and asked for the whole cluster to be consolidated in float/ so it can be worked in one session. This ticket's only content the umbrella did not already have — the deliberate Single+Double-only RTL surface — is now workstream 4 there. Moved rainy-day/ → float/ in the same pass.