docs: renumber 4a's as-built ledger row P4-40 to P4-60

Phase 4a and 4b ran as parallel stacks off main, and both numbered
their first as-built ledger row P4-40 -- 4a's one row (_ContextHost)
and 4b's ten (P4-40-P4-49). 4b merged first (#53-#55), so its numbers
stand on main; 4a's row moves to P4-60, with P4-50-P4-59 reserved for
phase 4c, which builds on 4b's tip. The design addendum, the checklist
and the roadmap's status note say what the row was called while the
lanes overlapped and why it moved, so the history stays readable.

Author: Wahbeh-Mohammad

docs/work/mvp/2026-09-05-ruby-sdk-v1-roadmap-design.md

@@ -2881,8 +2881,9 @@ object model, none removed — holds every reader of the five value types. One p
 plan's fence: `Context.validate!` is the private `#validate_context!`, since the design gives `Context`
 exactly one public method. Seventeen departures from the plan's text are itemised in the checklist, none
 lowering a gate. `_ContextHost`, the self-type interface strict Steep needs for `Context#close`, is the one
-new ledger row, **P4-40** — numbered from the tree, because 4b's design filed P4-12–P4-25 and 4c's
-P4-26–P4-39 before this phase executed. `docs/sdk-documentation/execution-context.md` is the as-built
+new ledger row, **P4-60** — numbered from the tree, because 4b's design filed P4-12–P4-25 and 4c's
+P4-26–P4-39 before this phase executed, 4b's as-built addendum took P4-40–P4-49 and P4-50–P4-59 are
+4c's; it was P4-40 while the two lanes ran in parallel and was renumbered before the push. `docs/sdk-documentation/execution-context.md` is the as-built
 page, every fence run verbatim on 4.0.6 and 3.2.11 with identical output; `architecture.md`, the core
 README, `README.md` and `docs/README.md` point at it. The design's ledger gains an "As built" addendum;
 the two postponed items keep their owners (the cap's configuration source, phase 5a Task 13; the no-op
@@ -2894,6 +2895,6 @@ returns as its own code → tests → docs stack. The counts that changed: `gems
 beside phase 0's `version.rb`; `phase4/phase4a/` now carries its checklist, the sixth written; the surface
 manifest is 580 lines; the cop suite is 129 cases. `CLAUDE.md`'s built-phases paragraph, its gem and
 phase-directory sentences and the constraints-that-bite list are rewritten from what was built. The
-consolidation of P4-1–P4-11 and P4-40 into design §10, and §5.4's and §8.1's addenda, are a human's, as
+consolidation of P4-1–P4-11 and P4-60 into design §10, and §5.4's and §8.1's addenda, are a human's, as
 they were for 3a and 3b: `docs/sdk-design-ruby/` is frozen, and `docs/deviations.md` is left as phase 2
 left it for phase 10 to flip.

docs/work/mvp/phase4/phase4a/2026-09-08-phase4a-execution-context-checklist.md

@@ -329,9 +329,11 @@ this build's.
   names as the owner of the two-factories distinction, is where the wording is next touched.
 - **The design's ledger** gains an "As built" addendum (in the design) for the eighth-cop numbering
   (P4-10), the two `sig/` mirrors (P4-3), `_ContextHost` (P4-2), the private validation (P4-11) and
-  the confirmed `#tracer` arity (P4-8), with the one new row numbered **P4-40**, the next free
+  the confirmed `#tracer` arity (P4-8), with the one new row numbered **P4-60**, the next free
   number in the phase-4 ledger the three sub-phases share (4b's design filed P4-12–P4-25 and 4c's
-  P4-26–P4-39 before this phase executed). The consolidation into design §10 and the §5.4 and
+  P4-26–P4-39 before this phase executed; 4b's as-built addendum took P4-40–P4-49 and 4c's is
+  reserved P4-50–P4-59 — the row was numbered P4-40 while the lanes ran in parallel and renumbered
+  before the push). The consolidation into design §10 and the §5.4 and
   §8.1 addenda are a human's, as they were for 3a and 3b, because `docs/sdk-design-ruby/` is
   frozen; `docs/deviations.md` is left as phase 2 left it for phase 10 to flip.
 

docs/work/mvp/phase4/phase4a/2026-09-08-phase4a-execution-context-design.md

@@ -1250,18 +1250,20 @@ the phase-4 segmentation design left the ledger empty.
 
 ### As built, 2026-09-16
 
-The plan added no numbered row; execution adds **one**, numbered **P4-40** because the phase-4
+The plan added no numbered row; execution adds **one**, numbered **P4-60** because the phase-4
 ledger is shared across the three sub-phases and the next free number is read from the tree, not
 assumed: phase 4b's design filed P4-12–P4-25 and phase 4c's P4-26–P4-39, both before this phase
-executed, and 4b is running as a parallel stack whose additions, if any, take the numbers after
-this one.
+executed; 4b, built as a parallel stack and merged to `main` the same day (#53–#55), took
+P4-40–P4-49 for its own as-built rows, and P4-50–P4-59 are reserved for 4c's, which builds on
+4b's tip. This row was first numbered P4-40 while the two lanes ran side by side and was renumbered
+before the stack was pushed, so no two rows share a number on `main`.
 Five rows above read slightly differently against the source; the difference is recorded here
 rather than by rewriting the text it corrects. The checklist's "Deviations from the plan" is the
 itemised list, and its "Guards run red" section holds the battery.
 
 | # | Deviation | Requirement / document | Why |
 |---|---|---|---|
-| P4-40 | A fourth RBS interface, `Dexpace::_ContextHost`, the self-type constraint of `module Context` | `NFR-4`; `NFR-3`'s strict `core` target; P4-2's list | `Context#close` calls `store` and `call_key`, which the module does not define and every includer does. The strict target types a module's `self` by its self-type constraint — the shape phase 1 gave `Model : _ModelInstance` — so `_ContextHost` includes `_ModelInstance` and adds the two readers, and `#close` types without an `untyped` receiver. It is a public name in `sig/`, locked with `_Span`, `_Tracer` and `_TracerFactory`; `store` stays `untyped` inside it, as on every flavour, because the runtime check is `respond_to?` and strict Steep refuses that on an interface type (3a) |
+| P4-60 | A fourth RBS interface, `Dexpace::_ContextHost`, the self-type constraint of `module Context` | `NFR-4`; `NFR-3`'s strict `core` target; P4-2's list | `Context#close` calls `store` and `call_key`, which the module does not define and every includer does. The strict target types a module's `self` by its self-type constraint — the shape phase 1 gave `Model : _ModelInstance` — so `_ContextHost` includes `_ModelInstance` and adds the two readers, and `#close` types without an `untyped` receiver. It is a public name in `sig/`, locked with `_Span`, `_Tracer` and `_TracerFactory`; `store` stays `untyped` inside it, as on every flavour, because the runtime check is `respond_to?` and strict Steep refuses that on an interface type (3a) |
 
 - **P4-10, as built.** `Dexpace/NoWeakReferences` is the **eighth** custom cop, not the seventh:
   seven exist on `main` — phase 0's five, `Dexpace/NoKeywordSplat` (phase 0, 2026-09-13) and