fix(ci): collapse multiline expression in cross-version-smoke workflow

[maphew]

Problems fixed

1. Workflow YAML parse error (original fix)

The VERSION_COUNT env value used a multiline plain YAML scalar — invalid YAML that caused GitHub to reject the file at 0s with "workflow file issue" on every push to main:

# BEFORE (invalid — plain scalars cannot span lines)
VERSION_COUNT: ${{
  github.event_name == 'push' && '30' || ...
}}

# AFTER (single line, same semantics)
VERSION_COUNT: ${{ (github.event_name == 'push' && '30') || ... }}

2. Smoke test CWD (root cause of all 5 upgrade scenarios failing)

All bd invocations ran from the test script's CWD (the checked-out beads repo), not from the isolated workspace $WS. This caused:

• bd init to detect the beads repo's origin remote (which has refs/dolt/data) and clone the entire beads Dolt database into $WS, corrupting the upgrade scenario and wasting ~2 minutes on chunk downloads
• git config beads.role to be written to the beads repo's git config instead of $WS's, so scenario 4's role check always failed

Fix: added prev() and cand() helpers that cd "$WS" before running any bd binary.

3. create --silent not in binaries older than ~v1.1.0

--silent was added after the v1.0.0 release; calling it with older release binaries silently failed, making every create attempt look like an init failure.

Fix: prev_create() helper tries --silent first, falls back to parsing any ID-like token from plain create output.

4. Mode preservation check used wrong path

Embedded Dolt stores data in .beads/embeddeddolt/ (a directory). The test checked for .beads/beads.db (a file), which never exists in embedded mode — so "DB exists before/after upgrade" always failed.

Fix: embedded_db_exists() checks for either the directory (current embedded mode) or the legacy SQLite file.

5. issue_prefix not sanitizing dots (TestEmbeddedInit/prefix_dot_sanitized)

When a prefix like GPUPolynomials.jl is passed, the DoltDatabase name was correctly sanitized to GPUPolynomials_jl but the issue_prefix stored in the DB still had the dot, causing issue IDs like GPUPolynomials.jl-1 and failing the readback test.

Fix: apply the same dot→underscore sanitization to issue_prefix in cmd/bd/init.go.

Test plan

• Resolve versions to test job passes (YAML fix)
• All 5 upgrade smoke scenarios pass for v0.60.0–v1.0.0
• TestEmbeddedInit/prefix_dot_sanitized passes
• No other regressions in CI or Regression Tests

🤖 Generated with Claude Code

[maphew]

CI notes

The YAML fix works: Resolve versions to test now passes (previously failed at 0s with "workflow file issue" before any jobs ran).

Smoke test failures are pre-existing, not caused by this PR:

• All versions (v0.60.0–v1.0.0) fail at init — the old binaries can't create issues after the recent init/bootstrap refactor (c96008f9, 1684130a). These failures were hidden before because the multiline YAML expression prevented the workflow from parsing at all.
• TestEmbeddedInit/prefix_dot_sanitized (Embedded Cmd 20/20) is also pre-existing; this PR only touches .github/workflows/cross-version-smoke.yml.

The smoke test upgrade-compat regression should be tracked separately.