feat: per-call project/project_id routing on bm_* tools

[groksrc]

Summary

Every `bm_*` tool now accepts optional `project` (name) and `project_id` (UUID) parameters. `_translate_args` layers the override on top of the configured default: `project_id > project > provider._project`. Only one of the two ever reaches BM, with `project_id` winning when both are passed — UUID is the unambiguous form across cloud workspaces (the disambiguator BM itself documents in `list_memory_projects`).

Routing properties live in a single shared `_PROJECT_ROUTING_PROPS` constant applied to every entry in `TOOL_SCHEMAS` via a post-construction loop, so the param shape stays DRY and a new tool can't be added without inheriting routing automatically. `system_prompt_block` mentions the cross-project capability so the agent reaches for these params when the user names a project that isn't the active one.

Addresses friction documented in "Hermes Basic Memory Cloud Task Experience": the original failure mode was the agent silently operating against the active Hermes memory project when the user asked for a write to a different cloud project (`main` on personal workspace). With this change the agent can route per-call without reconfiguring the plugin.

First of four planned changes from that note. Follow-ups (tracked as separate tasks): `bm_projects` / `bm_workspaces` as agent tools, a `bm_import` tool for file-on-disk → BM-note, and SKILL.md doc updates for the cross-project workflow.

Test plan

• Unit suite passes (`uv run --with pytest pytest`) — 236 passed, 12 skipped (integration, gated).
• 14 new tests in `test_helpers.py` cover: default-when-no-override, project-name override, project_id override, both-passed precedence, non-string coercion, every-tool parametrization (all 8 tools), and a schema-shape regression test asserting every `bm_*` tool advertises both routing props as optional.
• Smoke-test on a live Hermes session with two BM projects: call `bm_search(query=..., project="")` and `bm_write(..., project_id="")`, confirm the writes land in the targeted project. (Manual — depends on the deploy.)

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