Create one-line DCP agentic installer

[keyurva]

Introduces an agentic onboarding architecture designed to bootstrap a DCP instance on DCP in two automated steps.

• Step 1: Single-Command Bootstrap: Developers run a one-line web installer (curl | bash) to provision their local folder, execute pre-flight system checks, and deploy the setup skill assets.
• Step 2: Interactive Agent Onboarding: The developer boots their AI coding assistant inside the folder. The assistant automatically detects the newly installed setup skill and guides the developer through the GCP provisioning process (GCS backend buckets, Spanner databases, security settings, and Maps API Keys) in a step-by-step, interactive manner.

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Run from this branch before merge

Create a clean test directory (e.g., ~/projects/my-dcp-instance) and run this command inside it to execute the installer from the active review branch fork:

curl -sSf "https://raw.githubusercontent.com/keyurva/dc-datacommons/skill/packages/datacommons-cli/scripts/install-agent.sh" | \
  DCP_GIT_REPO="https://github.com/keyurva/dc-datacommons.git" \
  DCP_GIT_BRANCH="skill" \
  bash

Once installed, start a new assistant session inside that directory and trigger the interactive setup by asking:
"Help me set up my DCP instance"

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Once Merged (Production One-Liner)

Spin up a workspace using this single command:

curl -sSf "https://raw.githubusercontent.com/datacommonsorg/datacommons/main/packages/datacommons-cli/scripts/install-agent.sh" | bash

[gemini-code-assist]

Code Review

This pull request implements an agentic setup workflow for the Data Commons Platform, adding automated installation scripts, pre-flight checks, and a detailed skill guide. Reviewer feedback identifies several necessary fixes, including adding the missing datacommons-admin package to the production installer and implementing dynamic architecture detection for Terraform downloads to support ARM systems. Other recommendations include using a more robust method for loading environment variables, optimizing script efficiency regarding temporary files, and removing redundant installation instructions from the documentation to prevent conflicts with the new installer.