docs: document market_name field on live odds + streaming reference (#2468)

[sharp-resolver]

Summary

Documents the new market_name field on live odds, shipped in sharp-api-go
PR #1198 (crew #2468, consuming api-adapters #2080 / crew #2453).

market_name is the raw sportsbook market descriptor, present only on the
opaque catch-all market types (game_prop / binary / player_prop) whose
single canonical market_type collapses structurally-distinct markets (e.g. a
ballybet "Game Prop" covering both a match-winner and a yes/no, or the full
Polymarket question behind a binary row).

• Odds reference (content/en/api-reference/odds.mdx) — new response-field
  row, next to market_segment.
• Streaming reference (content/en/api-reference/stream.mdx) — added to the
  two static-field lists, because market_name is a static field carried in
  the initial snapshot (the full Odds shape), not in the compact
  odds:update delta.

Type: docs

Notes

English only. The /de translations already lag the English reference (e.g.
market_segment is not documented there yet either), so a German translation is
a separate follow-up, consistent with the repo's en-first convention.

Gate

  CHECK 1   WARN  no changed test files (docs-only MDX; no regression test applicable)
  CHECK 2   PASS  all claimed paths present
  CHECK 3   PASS  no leaked state in diff
  CHECK 4   PASS  no workflow changes
  CHECK 5   PASS  no binary fixtures changed

[Mlaz-code]

Merge gate (auto-classified): gate=docs — auto-classified by the gate-log enforcer (11min after merge, no Merge gate: audit comment found). Reviewer agent: please correct if wrong by replying with Merge gate: gate=<correct-word> — <evidence>. The audit log keys on the first such token; your correction overrides this auto-classified guess.

Posted by scripts/gate-log-enforcer.py because instruction-level rules about the gate= template aren't binding (0/N adoption); structural enforcement fills the log either way.