pkg/linker: link share/terminfo for keg_only formulas

Fixes nano and other terminal UI apps failing with 'cannot initialize terminal type'
when relying on keg_only ncurses.

fix test case

remove unnecessary build step

feat(linker): link share/man and share/info into the prefix

Remove the policy of stripping man pages and info pages. The installer
no longer prunes share/man and share/info from the keg before capturing
the manifest snapshot, and the linker no longer skips those entries when
populating share/. Both subdirectories are now linked like any other
share/ content — share/man/manN/ sections and share/info/ are
materialized as real directories so multiple formulas can coexist.

Also remove the associated audit warning that flagged these directories
as unsupported, and the reset-update cleanup block that deleted them
from the system prefix. The shellenv MANPATH/INFOPATH exports were
already correct and need no change.

Add debug logging to LinkWithOpts, UnlinkWithOpts, linkDirWithOpts, and
unlinkDirWithOpts for opt-link lifecycle, shared-dir materialization,
symlink-to-dir expansion, and per-file link/unlink events.

Update README, docs/tech.md, and pkg/linker/doc.go to reflect that
share/ now includes man pages and info documents.

security: root keg source traversal and unsymDir read through os.Open…

…Root

linkDirWithOpts: replaced os.ReadDir(srcDir) with os.OpenRoot(srcDir) +
fs.ReadDir(srcRoot.FS(), ".") at every call level (including recursive
ones). Closes the TOCTOU window between the caller's e.IsDir() check and
the subsequent ReadDir — if a keg directory entry is raced to a symlink
pointing outside the keg between those two operations, os.OpenRoot now
refuses to follow it.

unsymDir: replaced os.ReadDir(safeTarget) with os.OpenRoot(absRoot) +
fs.ReadDir(unsymRoot.FS(), rel), using the relative path already validated
by the preceding isWithinRoot and SafeJoin guards. Pins the directory read
to the trusted prefix root fd rather than re-traversing the string path.

fix(shellenv): align MANPATH and FPATH behavior with Homebrew

update GEMINI.md and README.md for post-v0.7.27 changes

- regenerate GEMINI.md with accurate command surface, architecture,
  security primitives, and testing conventions
- add distclean to GEMINI.md build commands
- update README.md: universal binary, path-traversal hardening,
  build-fat-binary and distclean targets, remove completed roadmap item

Merge branch 'fix/tcl-tk-source-build'

Source builds now honor build.working_dir + configure/install command
overrides; genrepo stamps build.working_dir=unix onto tcl-tk / tcl-tk@8.

feat: install accepts multiple args with --formula/--cask selection

grew install now takes one or more arguments and auto-detects each as a
formula or a cask (formula takes precedence). The mutually-exclusive
--formula and --cask flags pin every argument to a single kind and disable
the other. Arguments are processed in order; installation stops at the first
failure.

Enforce the count with cobra.MinimumNArgs(1) and the flag exclusivity with
MarkFlagsMutuallyExclusive. Refactor RunInstall into per-arg dispatch
(resolveInstallKind / installFormulaArg / installCaskArg), close a latent gap
where --dry-run --cask installed anyway, and add smoke tests plus doc updates.

Fix completion cache initialization to support dynamic cacheDir param…

…eter

Previously, cacheDir was ignored (kept for signature compatibility).
Now, when cacheDir is empty, it's dynamically resolved to the system cache dir.
When provided, it's used directly (for testing or custom locations).