fix(spawn): convert team config paths for readfile() via agmsg_sql_readfile_path

[chemica-tan]

Summary

resolve_team in spawn.sh is the only readfile() caller that passes a raw sed-escaped path into SQL. Every other caller (join.sh, whoami.sh, identities.sh, api.sh, resolve-project.sh) already goes through agmsg_sql_readfile_path, which cygpath-converts the path on Windows and SQL-escapes it. This PR aligns spawn.sh with them (1 line) and adds a regression test.

Symptom / minimal reproduction

Environment: Windows, Git Bash, a native Windows sqlite3.exe first on PATH (e.g. the WinGet build — sqlite3 3.53.3).

A native sqlite3.exe cannot readfile() a POSIX-form path (/tmp/..., /c/...): it returns NULL, the JSON probe yields no rows, and spawn dies with no team is registered even though join.sh just succeeded:

$ ./scripts/join.sh myteam alice claude-code "$PWD"
Joined team myteam as alice
$ ./scripts/spawn.sh claude-code bob --project "$PWD"
spawn: no team is registered ...

In normal use the bug is masked because registrations usually hold C:/-form project paths — but the bats suite runs under a POSIX-form $TMPDIR, so on such a machine every join→spawn test fails (38 failures for us). With this fix the suite is green again (remaining failures on our machine are unrelated, pre-existing environment issues).

• agmsg version: v1.1.7 (also reproduced on v1.1.6)
• host agent: Claude Code (found while running the test suite; diagnosis cross-checked by a Codex reviewer)

Change

• scripts/spawn.sh: cfg_sql=$(printf '%s' "$config_file" | sed "s/'/''/g") → cfg_sql=$(agmsg_sql_readfile_path "$config_file") (the variable feeds both queries in the loop, so one line covers both)
• tests/test_spawn.bats: source-level regression assert. No portable runtime probe exists — it would need a native sqlite3 plus a POSIX-form tmpdir — so the test pins the helper usage directly, with a comment explaining why.

The single-quote behaviour is preserved: the helper SQL-escapes exactly like the old sed, and spawn: team resolution survives a single quote in the project path still passes.

Tests

$ bats tests/test_spawn.bats -f "team"
1..6
ok 1-6 (including the new regression test)

🤖 Generated with Claude Code

https://claude.ai/code/session_013Hh8w1h5CJJH77a6N4gwN2