Remove empty EU1.1 bootstrap coverage placeholder

[Zection6V]

Summary

Removes the obsolete coverage/eu11-bootstrap-entry-points.json placeholder without dropping EU1.1 exact-content/AOT support.

The deleted file contained no ARM9 or ARM7 entry points; it only carried the EU1.1 SHA-1 so the old required --coverage path would accept the profile.

Changes

• delete coverage/eu11-bootstrap-entry-points.json
• represent EU1.1 as coverage: "" until real coverage is promoted
• make top-level CMake treat static coverage as optional per exact-content profile
• make tools/prepare_mph.py --coverage optional
• when coverage is absent, seed only the ROM-header ARM9/ARM7 entry points, which is equivalent to the deleted empty manifest
• keep US1.0's real promoted coverage unchanged
• update the multi-ROM checker to reject reintroduction of the empty EU1.1 placeholder while synthesizing a temporary legacy-compatible manifest only inside its test view
• update the EU1.1 bring-up documentation to describe the bootstrap-only state and the optional coverage workflow

Safety

• runtime seven-version detection is unchanged
• EU1.1 exact SHA/provenance metadata is unchanged
• EU1.1 exact AOT preparation remains possible; it simply bootstraps without fake static coverage until real coverage exists
• ROM-free Nightly behavior is unchanged
• future real EU1.1 coverage can be promoted to a normal manifest and referenced by the profile without changing the runtime model

Validation

Current head: e60bac604c0b846fd8834ceb52230e3b129d3bd9

• MPH Multi-ROM Static Checks #134: SUCCESS
  • profile/coverage schema validation: SUCCESS
  • melonPrimeDS detector/widescreen cross-check: SUCCESS
  • runner patch idempotency and translation-unit compile: SUCCESS
  • seven-version runtime dispatch: SUCCESS
  • exact-content ROM checker configure/build path: SUCCESS
• Build #47: SUCCESS
  • ROM-free release policy: SUCCESS
  • Linux ROM-free runner + generic-config startup smoke test + AppImage: SUCCESS
  • Windows ROM-free runner + generic-config startup smoke test + launcher tests + ZIP: SUCCESS