Restate C-004, C-005 and C-200 as ADR-0024's sequential run-every-element observation

[O6lvl4]

What

Step 0 of almide ADR-0024 (docs/adr/0024-fan-effect-callbacks-run-concurrently-as-if-sequential.md, almide/almide#3028): the contract text for fan running concurrently while being observed as a sequential, run-every-element evaluation.

• C-004: fan.map and fan.settle behave as a sequential evaluation of every element in list order, whatever the substrate. The EXCEPTION clause (block/settle interleaving on native) is kept; ADR-0024 step 1 deletes it when per-element output buffering lands.
• C-005: fan.map evaluates every element, including those after an Err, and the lowest-index Err surfaces (the rule fan { } already follows, C-199).
• C-200: a trap in element k is observed as the sequential evaluation: elements 0..k-1 complete and flush in order, nothing after k appears. A concurrent substrate waits for the elements below the trap (ADR-0024 D6). The residual is stated: an element above the trap that had already started may have sent requests the sequential evaluation never sends.
• ALS-R3 prose amended to match. Its validation row is re-stamped.
• The reference evaluator's fan.map now runs every element and returns the lowest-index Err.
• New fixtures: spec/wasm_cross/fan_map_err_runs_every_element.almd (C-005) and spec/wasm_cross/fan_trap_waits_for_elements_below.almd (C-200).

The contracts are ahead of the implementation. Judged locally against almide 0.64.0 (ref + cross legs):

• fan_map_err_runs_every_element: ref disagrees with both legs. Today's fan.map stops at the first Err, so it prints 2 of the 5 lines.
• fan_trap_waits_for_elements_below: ref agrees with wasm. Native races, and element 2's line appears in about 11 of 20 runs.

Both are expected findings against released binaries. almide does not advance proofs/als-pin.txt to this commit until the PRs that implement D1 (step 3) and D5/D6 (step 1).

Local gates, all green: check-contracts, contract-provenance, element-coverage, style, validation, links, gate-verification, selftest-conformance, runner-coverage, ref-independence, ref-kernel (49/49), ref-totality.

Author / verifier record

role	who (human handle, or agent + session)	independent of the author?
authored	Claude (agent, O6lvl4's session)	—
verified	Claude (same agent): local gates + ref/cross legs against almide 0.64.0	no

Ratchets loosened in this PR (ceiling up / floor down): none.