docs: clarify Homebrew tap copy

[daniel-scrivner]

Summary

Clarifies tap and formula descriptions without changing package source, version, checksum, or installation behavior.

Scope

• Formula/secapi.rb - Main secapi formula
• Formula/ - Other formula additions / updates
• README.md - Tap usage docs
• .github/ - CI/CD workflows / brew-test-bot config

Changes

• Updated Formula/secapi.rb description/copy only.
• Updated README.md tap usage copy to align public positioning.
• Preserved package source, version, checksum, dependency, and installation behavior.

Verification

Validation reported by Terra copy worker and GitHub checks:

Diff check - passed
brew style - passed
Ruby syntax - passed
Markdown link syntax check - passed
GitHub Actions Formula / secapi formula - SUCCESS

The prior warning/UNSTABLE state was classified as an environment warning, not copy-induced. This PR is still gated on exact GitHub check conclusions and mergeStateStatus before merge.

Deployment Impact

• Formula version bump (matches upstream release tag)
• SHA256 verified against the published artifact
• Tests pass on macOS (Intel + Apple Silicon if applicable)
• Tests pass on Linux (if formula supports it)
• Companion release shipped in secapi-ai/secapi-cli

Completion Attestation

• 100% complete, 100% functional for this documentation/formula-copy-only scope. All stated copy changes are written and validated; no source URL, checksum, version, dependency, install, or release behavior changes are included.
• Not fully complete or functional. Deltas listed below.

Screenshots / Demo

Not applicable: formula and README copy only.

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Agent Context

Key files to read first:

• Formula/secapi.rb
• README.md

Decisions made:

• Treated environment warning as non-copy-induced but did not relax merge gates.
• Kept formula source, version, checksum, dependencies, and install behavior unchanged.

Relevant docs:

• https://docs.brew.sh/Formula-Cookbook
• secapi-ai/secapi-cli upstream package

Conventions applied:

• Homebrew formula metadata/copy only.
• No release or artifact updates in this PR.