sales: add Grain to ~~conversation intelligence Included servers alongside Fireflies

[adams]

The sales/CONNECTORS.md table currently lists Fireflies (Included) and Gong, Chorus, Otter.ai (Other options) for the ~~conversation intelligence category. Grain (grain.com) is a sibling option in the same category and slots in cleanly via the existing tool-agnostic placeholder pattern.

Changes

• Add grain server block to sales/.mcp.json pointing to https://api.grain.com/_/mcp
• Add Grain to the "Included servers" column in sales/CONNECTORS.md alongside Fireflies. This matches the existing multi-included-server pattern in other categories in the same file — e.g., Clay, ZoomInfo, Apollo in ~~data enrichment, HubSpot, Close in ~~CRM, Google Calendar, Microsoft 365 in ~~calendar, Gmail, Microsoft 365 in ~~email.

What stays the same

No changes to any skill, agent, or command. The ~~conversation intelligence placeholders in call-prep/SKILL.md, call-summary/SKILL.md, and competitive-intelligence/SKILL.md all work as-is once Grain is wired.

Why this fits the plugin's coverage

Grain skews toward smaller sales teams and individual operators who don't run Gong/Chorus, and toward product-team workflows that overlap the sales plugin (customer-interview recordings consumed by competitive-intelligence). Today those users either install the sales plugin and have the transcript-consuming skills sit dark, or paste transcripts manually. Adding Grain to the Included list lets the existing skill suite work for them out of the box.

MCP details

Grain's MCP is publicly available at https://api.grain.com/_/mcp. Auth is OAuth via Grain account. Reference: https://grain.com/release-note/06-18-2025 and https://developers.grain.com.

Anticipated reviewer questions

• Why "Included servers" rather than "Other options"? The .mcp.json already ships both Fireflies and Grain after the patch — listing both in "Included servers" reflects what's actually bundled. Pattern is well-established elsewhere in this same file (multi-server "Included" cells in ~~CRM, ~~data enrichment, ~~calendar, ~~email). Happy to swap to "Other options" if you'd prefer the more conservative placement.
• Why placed after Fireflies rather than alphabetical? The existing server orderings in this file aren't alphabetical (e.g., HubSpot, Close for CRM). Placing Grain after Fireflies preserves Fireflies's existing primary position. Happy to reorder.
• Is the MCP production-grade? Yes — Grain's MCP launched June 2025, used by Grain customers, and is what Grain's own internal automation runs on. Same SLA as Grain's main product.
• Does this change default behavior for users without a Grain account? No. Both MCP servers require auth on first use — the plugin doesn't silently call any endpoint, and skills using ~~conversation intelligence only invoke MCP tools when the user has authenticated the relevant server.

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Linked to the coordinating issue covering this PR and the parallel product-management PR.

Refs #257