refactor(cli): remove the redundant --macd flag, superseded by --harness macd

The --macd flag was a back-compat alias for --harness macd, added in cycle 0065
iter-3 while the uniform `--harness <name>` selector was introduced. With that
selector in place the alias is pure redundancy, so drop it: --harness <name> is
now the sole way to pick a built-in harness.

Removed from parse_run_args: the macd_flag accumulator, its match arm, and the
(harness, macd_flag) conflict resolution -- harness selection collapses to
`harness.unwrap_or(HarnessKind::Sma)`. Both usage strings drop `[--macd]`; the
parse_run_args doc and the parse_real_args note no longer cite the flag.

The MACD harness itself is untouched: run_macd, the macd() composite, and
`--harness macd` all stay. Tests updated -- the alias test becomes a positive
`--harness macd -> Macd` test plus an assertion that `--macd` is now rejected as
an unknown token; the "repeated --macd" edge is dropped (the flag is gone, and
repeated-flag strictness is still covered by --harness/--trace).

INDEX.md: the two realization notes that documented `--macd` as a live run form
updated (`aura run [--real ...]`; `run --harness macd`). The historical
graph-viewer retirement note and the frozen fieldtest capture are left as the
record of their time.

Verified: clippy --all-targets -D warnings clean; full suite 513 passed / 0
failed (assertions rewritten in place, no test count change); live smoke --
`aura run --harness macd` emits a RunReport, `aura run --macd` exits with the
updated usage.

docs/design/INDEX.md

@@ -1115,7 +1115,7 @@ Recorded streams are sparse and timestamped (a record per fired cycle, tagged
 **Realization (the web-from-disk visual face, #101).** The C14/C22 web seam shipped
 (amendment 3b56efb): a recording run persists each drained tap as a columnar (SoA,
 C7) `ColumnarTrace` to `runs/traces/<name>/` (`aura-registry::TraceStore`, beside the
-run registry's `runs.jsonl`), reachable via `aura run [--macd] [--real <SYM> …]
+run registry's `runs.jsonl`), reachable via `aura run [--real <SYM> …]
 --trace <name>`; `aura chart <name> [--panels]` reads them back, aligns all taps on a
 synthetic-union timestamp spine via the post-run `join_on_ts` (C3 — not in-graph;
 C1 — pure, no live external call), and emits a static self-contained uPlot page
@@ -1189,7 +1189,7 @@ by key for determinism, C1); a family is its *first producer* — the deliberate
 step toward the programmable analysis meta-level (C21) **without** rebuilding the
 orchestration axes (that is its own later cycle). Name resolution is made a **total
 function** by the write-guard `TraceStore::ensure_name_free`, called once per tracing
-command (`run`/`run --macd`/`run --real` → Run; `sweep`/`mc`/`walkforward` → Family)
+command (`run`/`run --harness macd`/`run --real` → Run; `sweep`/`mc`/`walkforward` → Family)
 to refuse cross-kind name reuse — so the one ambiguous on-disk state (a name used by
 both a run and a family) is unreachable. Every error path exits 2, never panics
 (C18/C10 refuse-don't-guess). Engine untouched (C9/C14): the whole change is