roadmap: native-seven next action is the successor blocker chain

[gunbai-bot]

Rewrites the native-seven row's first_slice in gunbc.roadmap_authority to the current chain, replacing the stale N7-0..N7-5 ledger hand-off text instead of appending to it. The on/note revision fields are updated to match.

• Phase A (typed endpoint): the blocker chain in order — count (v2: bare count over lists binds the std.algebra collection size row, a stated Int (XL-2, N7) #13307) → bare filter; call result type (v2 infer: derive a call's result type from a declared return (instantiated, alias-normalized) #13325 with v2 native infer accepts variant-scrutinee matches (payload binder typing + coverage through the inhabitance relation) #13210); literal elaboration (v2 infer: an integer literal elaborates at an expected type through literal_homomorphism_rows; std.nat Peano row; -1 refused at Nat (XL-2) #13320); from_code_point (floor: read a revision's environment closure from that revision (base closure was taken from the head tree) #13408 → Floor judges base-revision facts with the base revision's own compiler #13453 → std.unicode.scalar: partial from_code_point (typed refusal) + char_text; migrate v2 callers #13378); kernel-text concat (v2: kernel-String concat through a free-monoid structure bound on the roster carrier (XL-2) #13284); Cardinality (v2.std.grammar: qualify the GrammarExpr Optional arm (N7 resolve link) #13379); Optional ambiguity (de-fork PR B); EmptyPattern; filesystem_io at lowering (XL-2).
• Phase B (execution): map/all iteration direction (N7-1b: std.algebra collection callback ops (map, all) realized through the one fold encoding, keyed on named template rows #13069), a v2 evaluation meaning for concat (v2: kernel-String concat through a free-monoid structure bound on the roster carrier (XL-2) #13284), NativeTestPassed rows (v2 native infer accepts variant-scrutinee matches (payload binder typing + coverage through the inhabitance relation) #13210).

Projection: first_slice is not rendered into ROADMAP.md. generated_artifact_gate main_wet on this head left every generated artifact byte-identical (BuildBuddy 3af787af…/regen run).

Target run, base main ea9a51c: BuildBuddy 38db1680-9612-4df4-8eff-0e7a6c512d59. All 8 refuse at prepare/infer with projection_receiver_declaration_unavailable, and extdeps/filesystem/filesystem_io.dag refuses at lowering (service_realization_unreachable). This PR changes no compiler input, so the head run is the same as the base run. Blocker movement: none (text only).

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