re: sub_822737C8 is the coroutine spawner; the record's third word is the MAIN ENTRY

Asking who calls the function the timeline calls enumerates every way an ISL routine
can begin.  sub_822737C8(phase, base, offset) computes base + offset early on, and has
seven real call sites: the phase initialiser sub_82270DF8, the built-in stub region
(start_coroutine), the timeline walker sub_822748D0, TWICE inside sub_8226D740 -- the
per-frame engine->script drain -- and two unread, sub_82273910 and sub_82264058.

CORRECTION to my own write-up: the 0x1883 record's third word is the phase's MAIN
ENTRY, not a "size".  The initialiser hands it straight to the spawner:

    8227101C  or  r5, r22, r22     ; the record's third word
    82271020  or  r4, r26, r26     ; the code base
    82271030  bl  0x822737C8

44 of 44 records land on the instruction stream (100%) against a 25.0% control, and
all three Stage-02 targets open with the identical prologue
`special[0]=0 ; local[0]=0 ; call builtin116(0)` -- a routine entry, not a length.
So the record is 0x1883, base, MAIN_ENTRY, 0, code_end, force_end_handler.

Seeding the main entries moves no coverage number: every one was already among the
CFG's entry points by another route.  This corrects a field's meaning, not the graph.

Lead recorded rather than claimed: both of the drain's spawns take their offset from
[node+112], the first field of a drained node to be located, and the best remaining
angle on the ~15% of code nothing appears to start.  It is NOT shown that those nodes
come from the trigger queue at phase+272 -- that is precisely the over-reach
isl-builtins.md already made and withdrew, so it is not asserted here.

All artefacts regenerate byte-identical; this is documentation only.

docs/re/isl-stream-entry-points.md

@@ -99,8 +99,25 @@ tag `0x19` = int, tag `0x1A` = IEEE float — and `entry_a` is where it starts.
 exceeds 0x18 is exactly that phase's `entry_a`. Zero exceptions.** Only two tags
 ever appear: 1 394 × `0x19` and 675 × `0x1A`.
 
-So the record is `0x1883, base, size, 0, code_end, force_end_handler` — one
-boundary and one entry.
+So the record is
+
+```
+0x1883, base, MAIN_ENTRY, 0, code_end, force_end_handler
+```
+
+🔴 **The third word is NOT a size** — that was my label and it was wrong. The
+phase initialiser `sub_82270DF8` passes it straight to the coroutine spawner:
+
+```
+8227101C  or  r5, r22, r22      ; r22 = the record's third word
+82271020  or  r4, r26, r26      ; r26 = the code base
+82271030  bl  0x822737C8        ; spawn(phase, base, word3)
+```
+
+Measured: **44 of 44 records land on the instruction stream (100 %) against a
+25.0 % control**, and all three of Stage 02's targets open with the identical
+prologue `special[0]=0 ; local[0]=0 ; call builtin116(0)` — a routine entry, not
+a length.
 
 🟡 The table's contents are **not decoded**. Its int values do land on the
 instruction stream more often than chance (46/51 vs 29.5 %), but **0 of them are