Remove em dashes where the replacement is unambiguous

The project has a standing style rule against em dashes that was missed
when these docs were written. This removes the 42 occurrences where the
substitution is mechanical and cannot change meaning:

- table cells using an em dash as a placeholder, now a hyphen
- em dashes immediately followed by a conjunction or subordinator
  (but, and, or, so, though, while, which, where, because, since),
  where a comma is simply correct

115 remain. Those join independent clauses, where a comma would create a
splice and a colon often reads wrong, so each needs a judgement call
rather than a pattern. A blanket regex over them was attempted and
reverted: it produced double colons and broken sentences.

docs/production-timeline.md

@@ -80,7 +80,7 @@ flowchart LR
 
 Printed jackets from a local carton partner typically need **10 to 20
 working days** from approved artwork. That fits comfortably underneath
-the metal path — but only if artwork lands early. When a label delivers
+the metal path, but only if artwork lands early. When a label delivers
 artwork after approving the test pressing, the jackets become the
 critical path and every day of metalwork saved is wasted.
 
@@ -101,16 +101,16 @@ no mastering room of our own.
 | # | Stage | Launch | Mature | Notes |
 |---|---|---|---|---|
 | 1 | Audio intake and technical QA | 1–2 | 1–2 | Checksums, format, levels, side-length vs format. Rejects here are cheap; rejects later are not |
-| — | **Gate: master plan approved** | *customer* | *customer* | 2–10 days in practice |
+| - | **Gate: master plan approved** | *customer* | *customer* | 2–10 days in practice |
 | 2 | Vinyl mastering | 3–7 | 2–4 | Launch: external engineer or partner. Mature: in-house room, and queue depth becomes ours to manage |
-| — | **Gate: master approved** | *customer* | *customer* | 2–10 days; more if the artist wants revisions |
-| 3 | Lathe cutting to lacquer | — | 1–2 | Includes test cut, groove microscope, dead-wax scribe |
-| 4 | Silvering and electroforming | — | 2–4 | Three generations plus XRF, metrology, mother listening check |
-| 5 | Stamper prep | — | 1 | Punch, back-finish, coin, concentricity |
-| 3–5 | **Outsourced cut + metal** (launch only) | 10–20 | — | Stamper Discs, Sheffield; queue is theirs, not ours |
-| — | **Stamper freight UK → TH + customs** | 3–7 | — | Air freight; nickel travels well, unlike lacquer |
+| - | **Gate: master approved** | *customer* | *customer* | 2–10 days; more if the artist wants revisions |
+| 3 | Lathe cutting to lacquer | - | 1–2 | Includes test cut, groove microscope, dead-wax scribe |
+| 4 | Silvering and electroforming | - | 2–4 | Three generations plus XRF, metrology, mother listening check |
+| 5 | Stamper prep | - | 1 | Punch, back-finish, coin, concentricity |
+| 3–5 | **Outsourced cut + metal** (launch only) | 10–20 | - | Stamper Discs, Sheffield; queue is theirs, not ours |
+| - | **Stamper freight UK → TH + customs** | 3–7 | - | Air freight; nickel travels well, unlike lacquer |
 | 6 | Press setup and test pressing | 1 | 0.5–1 | Mold change, stamper mount, warm-up, 10–20 TPs |
-| — | **TP to artist + gate: TP approved** | *5–15* | *5–15* | Courier plus listening time. The single largest customer-side block |
+| - | **TP to artist + gate: TP approved** | *5–15* | *5–15* | Courier plus listening time. The single largest customer-side block |
 | 7 | Production run | 1–5 | 1–3 | Throughput table below |
 | 8 | Finishing, assembly, packaging | 2–4 | 2–3 | Trim is inline; shrink and jacket assembly are labour-bound |
 | 9 | Fulfilment and dispatch | 1–3 | 1–2 | Bulk pallet, or per-parcel dropship on an ongoing basis |
@@ -128,7 +128,7 @@ Two things the table deliberately does not hide:
   The launch configuration is sound precisely because it never ships
   one: audio goes to Europe as a file, the lacquer is cut and plated in
   the same region, and only finished nickel stampers make the journey.
-  Any future arrangement that cuts in Thailand and plates abroad — or
+  Any future arrangement that cuts in Thailand and plates abroad, or
   the reverse — would be a quality risk, not just a slower schedule.
 
 ## Production run throughput
@@ -154,12 +154,12 @@ decision.** A plant running at 90% quotes 16 weeks with the same
 equipment that quotes 6 weeks at 50%. Any turnaround promise made to
 the market is implicitly a promise to hold spare capacity.
 
-Small runs invert the arithmetic — though not as sharply as it first
+Small runs invert the arithmetic, though not as sharply as it first
 looks. At 300 units on the semi-automatic line the run is **5 to 8
 hours**, most of a shift, once the 60–70% effectiveness above is
 applied; it is roughly an hour on the full mature fleet. What dominates
 a small order is not the pressing but the setup, the approvals and the
-assembly, all of which cost the same at 300 units as at 3,000 — which
+assembly, all of which cost the same at 300 units as at 3,000, which
 is exactly the boutique/color work the semi-automatic
 line exists to serve, per
 [pressing-line.md](equipment/pressing-line.md). Small runs are not