docs(feasibility): add standing feasibility assessment + seam-class/evidence-tier regularity matrix

Recon-level feasibility assessment of the -iser family (docs/FEASIBILITY.adoc)
with a machine-readable per-iser classification (docs/feasibility-matrix.toml):

- seam classes (injector / service / scaffolder) — an -iser may claim only
  what crosses its C-ABI seam
- evidence tiers T0-T3 (chapeliser's Provable lane as the family template)
- language bar L0-L3 for the estate languages (a2ml, k9, eclexia, ...)
- per-language verdicts for the focused set: a2mliser, k9iser, eclexiaiser,
  chapeliser, futharkiser, and the Idris2-as-ABI bet in both its scoping
  options
- README/ATLAS pointers to the assessment

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

Author: arena-agent

README.adoc

@@ -376,9 +376,19 @@ The GitHub Pages hub provides:
 All 29 -iser repos are scaffolded and functional. The architecture is
 defined, CLI commands work, manifest parsers are operational, and test
 suites are in place across the family. Domain-specific code generation
-logic is the current frontier — each -iser is being deepened with real
+logic is the current frontier — each -iser is being deepened with real
 codegen for its target language.
 
+Each -iser also carries a *feasibility classification* — what its seam
+can actually carry (injector / service / scaffolder) and how much of
+its promise is machine-checked today (tiers T0–T3). See
+link:docs/FEASIBILITY.adoc[the feasibility assessment] and its
+machine-readable form, `docs/feasibility-matrix.toml`. Per that
+assessment: the honest family promise is *verified binding generators
+and foreign-runtime services, each claiming only what crosses its
+seam* — not "superpowers without learning languages", which no C ABI
+can deliver.
+
 == Contributing
 
 See CONTRIBUTING for guidelines. All contributions must pass the full CI

docs/ATLAS.adoc

@@ -117,4 +117,6 @@ To create an aspect for a language that has no -iser yet, use the meta-framework
 
 * `theory/AOLD.adoc` — the design philosophy (languages as aspects).
 * `theory/iSOS.adoc` — the architecture (composing aspects).
-* `../README.adoc` — family overview, architecture diagram, full install/usage.
+* `../FEASIBILITY.adoc` — the feasibility assessment: seam classes,
+  evidence tiers, and per-language verdicts. The status note above is
+  its summary form.