Feat/augment tool aliases

[pablo-lamtenzan]

Summary

• add configurable mapping from physical Pi tool names to
  logical GitNexus augment kinds
• preserve existing behavior when no env vars are set
• add optional pi-lean-ctx preset for ctx_read,
  ctx_grep, ctx_find, and ctx_shell
• document alias configuration and recommended pi-lean-ctx
  coexistence

Problem

Auto-augment currently matches only fixed built-in Pi tool
names such as:

• read
• read_many
• grep
• find
• bash

That makes wrapper tools work inconsistently in additive
integrations like pi-lean-ctx, where calls may use:

• ctx_read
• ctx_grep
• ctx_find
• ctx_shell

Explicit gitnexus_* tools already work, but auto-augment
did not recognize these wrapper tool names.

Solution

Introduce small abstraction from physical tool name to
logical augment kind.

Logical kinds:

• read
• read_many
• grep
• find
• bash

Default aliases remain unchanged:

• read -> ["read"]
• read_many -> ["read_many"]
• grep -> ["grep"]
• find -> ["find"]
• bash -> ["bash"]

Add shell-friendly CSV env overrides:

• GITNEXUS_AUGMENT_READ_TOOLS
• GITNEXUS_AUGMENT_READ_MANY_TOOLS
• GITNEXUS_AUGMENT_GREP_TOOLS
• GITNEXUS_AUGMENT_FIND_TOOLS
• GITNEXUS_AUGMENT_BASH_TOOLS

Add optional preset:

• GITNEXUS_AUGMENT_PRESET=pi-lean-ctx

Preset expands to:

• read -> ["read", "ctx_read"]
• read_many -> ["read_many"]
• grep -> ["grep", "ctx_grep"]
• find -> ["find", "ctx_find"]
• bash -> ["bash", "ctx_shell"]

If preset and explicit env var both exist, explicit env
var replaces preset for that logical kind.

Implementation notes

• auto-augment hook now classifies tool names by logical
  kind before matching
• extraction still uses tool input arguments rather than
  parsing wrapper output formats
• unknown tools remain ignored
• explicit gitnexus_* tools unchanged
• patch kept intentionally small and focused

Documentation

Added README section:

• Configuring auto-augment tool aliases

Includes:

• per-kind env examples
• pi-lean-ctx preset
• override behavior
• recommended coexistence config:
  • LEAN_CTX_PI_MODE=additive
  • LEAN_CTX_PI_ENABLE_MCP=0
  • GITNEXUS_AUGMENT_PRESET=pi-lean-ctx

Testing

• npm ci ✅
• npm run lint ✅
• npm run typecheck ✅
• npm test ✅
• npm run build ✅

Additional test coverage includes:

• default classification behavior
• CSV env overrides
• preset behavior
• explicit env override over preset
• hook-level alias behavior for ctx_grep and ctx_read

Notes

• built-in read was already documented and covered by
  existing code/tests
• this PR focuses on generic alias support rather than
  broadening scope beyond that