fix(honcho): sanitize dotted host fallback in workspace_id (#26459)

[Tranquil-Flow]

What does this PR do?

When `HonchoClientConfig.from_global_config` falls back to `resolved_host` for `workspace` (no explicit `workspace` field in the host block or root), the resolved host is the dotted form `hermes.`. Honcho's API rejects this against the `^[a-zA-Z0-9_-]+$` regex with `string_pattern_mismatch`, and the plugin retries init once per minute, flooding the journal with warnings while memory is silently disabled.

This PR rewrites `.` to `_` on the fallback path only. Explicit user-set `workspace` values are passed through unchanged so configuration mistakes surface as real API errors instead of being silently masked.

Related Issue

Fixes #26459

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature
• 🔒 Security fix
• 📝 Documentation update
• ♻️ Refactor
• 🧪 Tests only

How was this tested?

Added regression coverage in `tests/honcho_plugin/test_client.py`:

• `test_workspace_id_sanitizes_dotted_resolved_host_fallback` — reproduces the reporter's exact path (no `workspace` field, resolved_host="hermes.fundraising", asserts workspace_id="hermes_fundraising")
• `test_workspace_id_preserves_explicit_dotted_user_value` — guards that explicit `workspace: "my.value"` is NOT rewritten (intentional opt-in)
• `test_workspace_id_unchanged_for_already_safe_host` — baseline regression guard

Full `tests/honcho_plugin/` suite green.

Scope notes (what was deliberately NOT changed)

• The `host_key` lookup format (used for indexing into `hosts."hermes.X"` blocks in `honcho.json`) is unchanged — only the workspace value sent to the Honcho API is sanitized. Existing installs with dotted outer keys keep working without migration.
• We did not bundle a legacy-key migration step: the issue reporter described a new-install path, and migrating existing keys would mutate user config silently. If demand surfaces, that can be a follow-up PR with explicit logging.
• We did not change `resolve_active_host` in `client.py` — the fallback only matters at the workspace_id construction site.

Checklist

• I have read the contributing guidelines
• My code follows the existing code style
• I have added tests that prove my fix is effective
• All new and existing tests pass locally
• No README changes needed

[alt-glitch]

Duplicate of #26478 which fixes the same issue (#26459 — dotted host fallback violates Honcho workspace_id regex). Both PRs sanitize dots to underscores on the fallback path.

[Tranquil-Flow]

Closing as graceful supersession by #26478 (@aqilaziz, opened 2026-05-15, ~1 day earlier). Both PRs sanitize dots to underscores on the fallback workspace ID path.

@aqilaziz's PR has substantially broader coverage (+232/-54 vs ours +55/-2) — additionally migrates legacy dot-form host blocks when the CLI writes profile-scoped config and includes profile-rename handling, docs, and CI stabilizers. Going with theirs. Thanks @aqilaziz.