Add the GoMEOS pin manifest and per-binding generator policy

[estebanzimanyi]

What

Adds the two artifacts that bring GoMEOS onto the ecosystem-wide per-binding generator policy (same treatment as JMEOS #29):

• tools/pin/compose-order.txt — GoMEOS's canonical, dependency-ordered fold manifest. main is the old hand-written 1.3-era cgo binding; the codegen-driven 1.4/-22a surface lives in open PRs. This file fixes the composing set/order and records the disposition of every open PR.
• GENERATION.md — the per-binding generator policy: GoMEOS owns its generator in-repo at tools/codegen.py; the single source of truth is the MEOS-API catalog; flat generated cgo wrappers; the hand-written binding is retired generate-then-retire (the last green-CI version is the equivalence probe).

Docs + manifest only — no code, no build impact.

Disposition of the open PRs (committer review)

Verified ancestry (git merge-base, this turn): #5 is the frontier (13 commits over main) and contains #2 + #4.

PR	Role	Proposal
#5 codegen/flat-wrappers-22a	extends the meos-idl codegen to all installed-public families on the -22a catalog	the frontier (contains #2 + #4)
#2 refactor/codegen-meos-idl (draft)	the IDL-driven generator tools/codegen.py	ancestor of #5 — carried in #5
#4 work/portable-aliases	portable bare-name dialect, 6 families	ancestor of #5 — carried in #5
#1 bump/meos-1.3	1.3 CGO header bump	likely superseded by #5; verify, then close
#3 bump/meos-1.4	1.4 bump (branch tip diverged from #5)	#5 is the -22a (1.4+) frontier; verify, then close

Why

Per the per-binding generator policy: each binding owns its generator + its own pin manifest, the single source of truth is the MEOS-API catalog, and generation converges to a zero-hand-written surface via generate-then-retire.