feat(ogar-doc-ir): the composition brick — DocNode/ObjectSlot/ResolutionMode/ogar:// (W1, canon-free)

The first compilable brick of the DocIr composition layer (#217 doctrine,
#218 grounding), placed per operator ruling A1 ("one ogar-doc crate; split
axis is STATE not direction"): a `compose` MODULE beside the observation
IR, never a sibling crate. The observation IR is untouched.

- Closed 5-kind `DocNode` vocabulary — Document/Section/Paragraph/Text/
  ObjectSlot, exactly the doctrine §7 slice scope; Figure/Table/PageBreak
  are a `doc-compose.v2` bump, never a silent widening. Exhaustive enums
  (renderer gets a compile error on an unhandled kind). NO domain
  variants — a Wall/WorkPackage enters only through a slot (§3).
- `ObjectSlot{target, class_view (named view), field_mask: u64,
  wide_mask_words: Vec<u64>, resolution, fallback}` — the A3 brick
  (ClassView x WideFieldMask) made addressable. Masks travel in wire form
  (word w bit b => position w*64+b, positions >= 64 native — the
  ogar-a2ui-frame precedent), typed at the contract membrane; the module
  stays serde-only, zero canon dependency (lands ahead of mints, like the
  observation IR did).
- `ResolutionMode{Live, Revision(u64), Snapshot([u8;32])}` + strict
  `ogar://app/class/id@{live|revision:N|sha256:hex64}` parse/format —
  every malformed input is a refusal; a missing resolution suffix has NO
  default.
- Load gate + structural validation: version marker `doc-compose.v1`,
  closed-vocab serde rejection, out-of-range id refusal, cycle refusal
  (iterative DFS, no recursion).
- RBAC posture pinned per grounding SA4: slot masks are a REQUEST; the
  fail-closed `requested & role` intersection is the resolver's job
  (ClassRbac enforcement is probe-gated, never assumed).

9 new tests incl. the doctrine-§7 proof shape (WorkPackage.description
composing Text + User/WorkPackage/Attachment slots), all three ogar://
arms round-tripping, seven URI refusals, wide-position and snapshot-
fallback serde round-trips. 16/16 crate tests green; clippy/fmt clean.

Deferred, named: DocOp (§4 editor authority — next brick); the FieldView
enum widening + (ClassId, mode) named-view registry (ogar-render-askama /
ogar-class-view side); ogar-render-typst.

Ledger: W1 status appended to D-DOCIR-COMPOSITION (same commit, board
hygiene).

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Author: claude