Add work-specific configs and enhance git/shell setup

- Add modular zsh configs: zshrc-dev for dev tools, zshrc-natera for work
- Add .gitignore to exclude private Natera config from version control
- Configure git commit signing and delta diff viewer in gitconfig
- Regenerate p10k.zsh with rainbow theme and improved visual settings
- Add HIST_IGNORE_SPACE option to prevent saving sensitive commands
- Document Natera machine setup with private config template in README

zshrc-natera

@@ -0,0 +1,33 @@
+# Natera-specific environment and tooling
+# Sourced last from .zshrc on Natera machines (when this file is present).
+# All Natera config lives here only.
+
+# PATH for Natera/Claude tooling
+export PATH="$HOME/.local/bin:$PATH"
+
+# Claude Code (Bedrock)
+export CLAUDE_CODE_USE_BEDROCK=1
+export AWS_REGION=us-west-2
+export ANTHROPIC_SMALL_FAST_MODEL_AWS_REGION=us-west-2
+export ANTHROPIC_MODEL="us.anthropic.claude-sonnet-4-5-20250929-v1:0"
+export ANTHROPIC_SMALL_FAST_MODEL="us.anthropic.claude-haiku-4-5-20251001-v1:0"
+export CLAUDE_CODE_ENABLE_TELEMETRY=1
+export CLAUDE_CODE_MAX_OUTPUT_TOKENS=4096
+export MAX_THINKING_TOKENS=1024
+
+# OpenTelemetry (Natera staging)
+export OTEL_METRICS_EXPORTER=otlp
+export OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf
+export OTEL_RESOURCE_ATTRIBUTES="user.email=$USER@natera.com"
+
+# Project-specific aliases
+alias workbench='cd ~/work/rosalis'
+alias core='cd ~/work/yalp-core'
+alias histo='cd ~/work/yalp-histology'
+alias pipeline='cd ~/work/yalp-pipeline-integration'
+alias assayapi='cd ~/work/yalp-assay-qc-api'
+alias assay='cd ~/work/yalp-assay-qc'
+
+# Sensitive values (AWS profile, OTEL endpoint, cert paths, refresh alias) are in zshrc-natera.private
+# Copy zshrc-natera.private.example to zshrc-natera.private and fill in. That file is gitignored.
+[[ -f ~/dotfiles/zshrc-natera.private ]] && source ~/dotfiles/zshrc-natera.private