fix(init): sanitize dots in metadata.json DoltDatabase and add early validation (#3128)

[jjgarzella]

Summary

Fixes #3128 — bd init in a directory with dots in its name (e.g. GPUPolynomials.jl, common in Julia development) silently produced a broken installation: the database was created under one name but metadata.json recorded a different name, causing every subsequent bd command to fail with a cryptic invalid database name error.

Root Cause

Two bugs in cmd/bd/init.go:

Bug 1 — metadata.json mismatch:
dbName sanitized both hyphens and dots → underscores (lines 430–431), but cfg.DoltDatabase (written to metadata.json) only sanitized hyphens (line 666). The comment above line 430 explicitly warns these must match — they didn't.

Bug 2 — unclear error for unsanitizable characters:
Characters like spaces, @, ! that survive all sanitization caused an error deep inside the storage layer with no actionable guidance.

Changes

• cmd/bd/init.go line 666: add dot → underscore replacement to cfg.DoltDatabase to match dbName sanitization
• cmd/bd/init.go after line 440: add early dolt.ValidateDatabaseName check with clear error message and --prefix hint when the auto-derived name is invalid

Before / After

Before:

$ cd GPUPolynomials.jl && bd init --quiet && bd list
Error: failed to open database: invalid database name "GPUPolynomials.jl"

After (dots — silently fixed):

$ cd GPUPolynomials.jl && bd init --quiet && bd list
No issues found.

After (unsanitizable chars — clear error):

$ cd "my project" && bd init --quiet
Error: directory name "my project" produces an invalid database name "my project".
Re-run with a valid prefix: bd init --prefix <name>
(Database names must start with a letter or underscore and contain only letters, digits, underscores, or hyphens.)

Test Plan

• bd init in a *.jl directory succeeds and bd list works after
• metadata.json dolt_database field contains no dots after init in dotted directory
• bd init in a directory with a space fails immediately with message containing --prefix
• Existing --database flag validation path unaffected
• bd init --prefix myname in any directory still works as before

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Note: this is JJ's first time making a PR to beads with an AI agent, so if anything is wrong, we would appreciate feedback!

🤖 Generated with Claude Code

[maphew]

Thanks @jjgarzella — great first PR to beads! 🎉

Clean fix, solid tests, and the error message for unsanitizable directory names is a really nice touch. Welcome aboard!