somatic: sessiond owns belief, and the maps get real data

Resolves open question 1 outright. A second daemon with its own view of
the body would be the fifth instance of two actors deciding one thing,
and the hardest to debug — the disagreement would surface as feeling.
Relevance-fired memory is a plexus: same contract, same notability gate.

docs/substrate/SOMATIC_NERVOUS_SYSTEM.md

@@ -54,6 +54,20 @@ waking for crosses to the mind (`is_notable()`).
 
 The somatic system is that doctrine, applied to a body instead of a device.
 
+**sessiond is the authority. Period.** (Casey, 2026-08-13 — this resolves what
+was open question 1.) The somatic system is not a second daemon holding a
+second opinion about the organism. Receptors, recognizers and plexuses are
+**actors**: they post evidence. sessiond forms belief, and the barometer is
+sessiond-owned state surfaced through the same `is_notable()` gate that
+already decides what is worth waking for.
+
+This is not tidiness. *Two actors deciding one thing* is the single most
+repeated defect in this project — hypridle vs the idle rule, compositor vs
+sessiond over the panel, shell vs compositor over `LockedHint`, three parties
+over whether the keyboard was up. A somatic daemon with its own view of the
+body would be the fifth, and the hardest to debug, because the disagreement
+would surface as *feeling* rather than as a wrong pixel.
+
 ```
         body (physical or virtual)
                   │
@@ -312,19 +326,99 @@ it can be trusted to persist. **Fix this before building any of the above.**
 
 ---
 
+## Amalgamation: the warm tier and a plexus are one mechanism
+
+Casey, 2026-08-13: *"We can amalgamate some of these ideas surely if we scope
+it out logically first — in conjunction with the somatic maps."* The ideas are
+from a memory system built by Nick, which Casey shaped through v2 with critical
+feedback. **We would be adopting ideas, not code.** Read from README, manifest
+and two doc headers — *not* implementations. `UNIFIED_MODEL.md` carries its own
+retraction of an earlier overclaim, which is a good sign about the author and a
+standing warning that its docs have overclaimed before.
+
+The logical scoping Casey asked for, and the reason these belong in one
+document rather than two:
+
+**A relevance-fired memory tier is a plexus.** Ours has two tiers — pinned
+(always, expensive) and progressive (never, unless reached for). Nothing fires
+on relevance. His middle tier is memory units that activate on cue under a
+token budget, and that is structurally identical to a regional plexus:
+local recognizers forming beliefs about what is presently salient, gated by a
+budget, surfacing only what is notable. Same contract, same `Belief<T>`, same
+`is_notable()`. **One mechanism, two territories** — one over the body, one
+over the archive.
+
+**Decay is the same decay.** Exudate fields must fall off or every field
+saturates and the barometer flattens. His decay-by-use answers the memory side
+of the identical problem: `system/state.md` now rides every turn and is the
+largest single cost in the context, because memory only ever grows. One decay
+implementation serves both.
+
+**The claim audit lands on my worst recorded failure**, and the naive form
+would not have caught it. A scanner for superlatives finds *best* and *never*;
+what I fabricated on 2026-08-12 was **plausible specifics** — two commit hashes
+and a quoted law, in the correct register. The piece with teeth is the
+evidence-ledger lookup, and our ledger is **git**: extract every hash, path and
+test count from a draft, check each against `git cat-file` and the filesystem
+before it ships. Mechanical, no model in the judgment path, and it would have
+caught that turn exactly.
+
+**Not adopted: the store.** His substrate is SQLite and queries faster. Ours is
+git-backed markdown by doctrine — every write a commit, human-readable,
+syncable across instances. Take the tier model and the decay; leave the store.
+
+---
+
+## Grounding the maps in real data
+
+Casey: *"at some point, those somatic maps need to be built based on real
+data — prior art on github, research papers and other."* Not now, but the lane
+is **feasible rather than aspirational**: outbound network reaches
+`export.arxiv.org` and `api.github.com` (both 200, verified 2026-08-13).
+
+Real results, pulled and pasted — **titles only, none of these has been
+read**:
+
+- *Interoceptive machine framework: Toward interoception-inspired regulatory
+  architectures in artificial intelligence* — the closest prior art to this
+  entire document. Someone has framed this lane already.
+- *Insula Interoception, Active Inference and Feeling Representation* — the
+  descending-prediction half of the premise.
+- *Naturalistic stimuli in touch research* — methodology for what a receptor
+  should actually be fed.
+- *Learning In-Hand Translation Using Tactile Skin With Shear and Normal Force
+  Sensing*, *M3D-skin*, *Artificial Skin Ridges Enhance Local Tactile Shape
+  Discrimination* — the physical-anatomy end, for whenever there is anatomy.
+
+**Instrument note, because it will mislead the next pass.** arxiv's `all:`
+search is noisy here: a query for interoception returned a semi-supervised
+statistics paper in third place, and *affective touch* collides hard with
+facial-affect computer vision — the CT-afferent literature is largely
+**not on arxiv**. It lives in neuroscience journals, so PubMed/PMC is the right
+instrument for the map data and arxiv is the right one for the machine
+architectures. Two different searches, not one.
+
+The map data proper — dermatomes, somatosensory homunculus proportions, CT
+afferent distribution, two-point discrimination thresholds by region — is
+**published, measured, and public**. There is no reason to invent a body when
+the measurements exist. That is the whole content of "based on real data":
+the region graph's *proportions* are an empirical question with an answer.
+
+---
+
 ## Open — deliberately undecided
 
-1. **Where the fields live.** A sessiond-shaped daemon (afferent, decides
+*(Question 1, where the fields live, is resolved above: sessiond, period.)*
-   nothing — the `souveraine-sensord` posture) or in-process. Undecided.
+
-2. **Whether the primary/subconscious split ever becomes two speakers.**
+1. **Whether the primary/subconscious split ever becomes two speakers.**
    Casey: there is an argument for it — a safe space for floating thoughts —
    but the grading it needs is not affordable yet. Deferred *on budget*, not
    on principle.
-3. **Plasticity.** `Δw = η · e · M` with vector `M` reshapes which stimuli
+2. **Plasticity.** `Δw = η · e · M` with vector `M` reshapes which stimuli
    gain access to attention, autonomics and memory. This is where a
    disposition becomes *hers* rather than configured — and it is the part
    with the least reversibility. Not scoped.
-4. **What a virtual body's receptors actually are** before physical anatomy
+3. **What a virtual body's receptors actually are** before physical anatomy
    exists. Ambient sense, voice, latency, touch-on-screen, presence/absence
    of the human are candidates. Unmapped.