feat: add environment-backed output target

[VimCommando]

Summary

• replace the ambiguous es:/ and elasticsearch:/ context targets with env:/
• resolve Elastic settings from the process environment, then .env, with CLI authentication taking precedence
• document and specify the behavior, and make the generated-ID integration test independent of parallel file order

Validation

• cargo test (195 passed, 5 ignored)
• cargo clippy --all-targets (0 errors; existing warnings remain)
• openspec validate --all --strict --json

[Copilot]

🟡 Changes recommended

.env loading currently occurs before validating the env:/index URI form, which can surface the wrong failure mode for malformed env: outputs.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR introduces an explicit env:/<index> Elasticsearch output target that resolves connection settings from ELASTIC_ES_URL / ELASTIC_ES_API_KEY (process environment first, then .env), and returns es:/ / elasticsearch:/ to configured-host resolution to remove ambiguity and namespace conflicts.

Changes:

• Add env:/<index> output dispatch and URL construction/validation using environment + optional .env loading.
• Update CLI startup to conditionally load .env and to apply environment API key fallback only for env:/... outputs.
• Add/adjust tests and documentation/specs, including making generated-ID integration tests independent of bulk operation ordering.

File summaries

File	Description
tests/index_template.rs	Makes the generated-ID/upsert CLI test resilient to parallel file discovery/order changes.
tests/env_output.rs	Adds CLI integration tests covering env:/ behavior, .env precedence, and error cases.
src/output/mod.rs	Adds env scheme dispatch and environment-based URL construction/validation.
src/main.rs	Loads .env only for env:/ output and scopes environment API key fallback accordingly.
README.md	Documents the new env:/index-name output and migration guidance.
openspec/specs/elasticsearch-environment-output/spec.md	Adds a formal spec defining env:/ syntax, precedence rules, and validation requirements.
openspec/changes/archive/2026-08-26-add-elasticsearch-environment-output/tasks.md	Tracks implementation and verification tasks for the new capability.
openspec/changes/archive/2026-08-26-add-elasticsearch-environment-output/specs/elasticsearch-environment-output/spec.md	Archives the spec snapshot alongside the change proposal/design.
openspec/changes/archive/2026-08-26-add-elasticsearch-environment-output/proposal.md	Records rationale, scope, and breaking-change note for the scheme migration.
openspec/changes/archive/2026-08-26-add-elasticsearch-environment-output/design.md	Documents design decisions (scheme reservation, .env scoping, precedence).
openspec/changes/archive/2026-08-26-add-elasticsearch-environment-output/.openspec.yaml	Adds openspec metadata for the archived change bundle.
CHANGELOG.md	Notes the new .env fallback and the scheme migration in Unreleased.
Cargo.toml	Adds the dotenvy dependency.
Cargo.lock	Locks dotenvy in the dependency graph.
.agents/skills/espipe/SKILL.md	Updates skill documentation/examples to use env:/ instead of es:/ / elasticsearch:/.

Review details

• Files reviewed: 14/15 changed files
• Comments generated: 2
• Review effort level: Lite

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[Copilot]

🟢 Approval recommended

The changes consistently implement env:/ dispatch with scoped .env loading, preserve auth precedence, and add targeted tests/spec/docs without introducing obvious behavioral regressions.

Review details

• Files reviewed: 14/15 changed files
• Comments generated: 0 new
• Review effort level: Lite