Add session-based command execution with persistent shell sessions and null-byte delimited command boundary detection. This enables running multiple commands on the same shell session with proper exit code capture.

New components:

• PipeTriple interface for transport-agnostic shell I/O (local shell now, SSH/WinRM future)
• SessionManager for session lifecycle (create, reuse, close)
• Execute capability with FlatBuffer schema for request/response
• Async task support with dedicated sessions per task
• shep-module-shell for arbitrary command execution
• shep-module-copy for file transfer via base64 encoding

Key design decisions:

• Modules are stateless command executors; they don't know or choose which host they run on. Shep analyzes the playbook, establishes sessions to hosts, and connects modules to those sessions.
• ExecuteRequest contains only: command, timeout_ms, env. No host or session fields - this prevents untrusted modules from targeting arbitrary hosts.
• Shep owns all routing decisions based on playbook analysis.

Implementation details:

• Command boundary protocol uses \0SHEP:%d\0 markers (null bytes ensure no collision with command output)
• Line ending normalization (CR+LF -> LF) for cross-platform consistency
• Sync tasks share default session per host; async tasks get isolated sessions
• Sessions automatically cleaned up after async task completion

Files added:

• internal/session/ (pipe.go, local_shell.go, session.go, manager.go)
• internal/host/execute.go
• modules/shell/main.go
• modules/copy/main.go
• flatbuffers/capabilities/execute.fbs

make doclink

Coverage

test refactor

• Test Refactoring: Consolidated duplicate tests into table-driven tests using a structured testdata/table/ directory - Inventory tests: Migrated 6 inline tests to table-driven format (simple-ungrouped, hierarchical-groups, group-vars, empty-group, ansible-examples, inherit-group)

- Playbook tests: Migrated 11 inline tests to table-driven format (simple-tasks, with-handlers, with-block, with-roles, with-import, multi-play, fqcn-modules, with-loop, pre-post-tasks, become, pass-loop-var-prefix)

- Task tests: Migrated 5 inline tests to table-driven format (simple-task, passing-task, main-tasks, empty-blocks, local-action)

- Each test case now consists of a .yml input file paired with an .expected.json file containing the expected parsed output

- Standalone edge case tests retained for: invalid YAML, empty requests, FlatBuffer round-trips, and error responses

Add shep-plugin-inventory with inventory capability

Implements the inventory plugin for parsing Ansible YAML inventory files and the shep inventory ls CLI command.

New Plugin: shep-plugin-inventory

• Declares inventory capability (version 1)
• Parses Ansible YAML inventory format
• Handles nested group hierarchies with children
• Collects host and group variables
• Deduplicates hosts across multiple group definitions

FlatBuffers Schemas

• flatbuffers/domain/inventory.fbs - Domain types: Var, Host, Group, Inventory
• flatbuffers/capabilities/inventory.fbs - InventoryRequest/InventoryResponse

CLI Commands

• shep inventory ls -i <file> - List hosts and groups
• shep i ls -i <file> - Short form
• --format json|yaml|text - Output format selection
• -v verbose mode shows full variable details

Tests

• Unit tests for YAML parsing and FlatBuffer round-trips
• Integration tests for full plugin lifecycle via host manager
• Tests against Ansible example inventory files

Documentation

• Added "FlatBuffers Generated Code vs Go Structs" section to AGENTS.md
• Explains rationale for plugin Go structs mirroring FlatBuffers types